hgrc.5: fix quoting of literal strings

The quotes would go wrong in many places due to differences between
asciidoc version 8.2.7 used by Benoit and 8.4.5 used by me. Between
those versions asciidoc stopped interpreting the content of `quoted
strings`, and so `*` would start bold text in the old version, but do
nothing in the new version.

To complicate things further, `\*` would escape the bold tag in the
old version, but in the new version the backslash was inserted
literally into the output (because the backtick quotes it).

I've now replaced backticks with non-quoting plusses and escaped
backslashes as appropriate.

doc/hgrc.5.txt

@@ -19,11 +19,11 b' FILES'
 
 Mercurial reads configuration data from several files, if they exist.
 The names of these files depend on the system on which Mercurial is
-installed. `\*.rc` files from a single directory are read in alphabetical
+installed. `*.rc` files from a single directory are read in alphabetical
 order, later ones overriding earlier ones. Where multiple paths are
 given below, settings from later paths override earlier ones.
 
-(Unix) `<install-root>/etc/mercurial/hgrc.d/\*.rc`::
+(Unix) `<install-root>/etc/mercurial/hgrc.d/*.rc`::
 (Unix) `<install-root>/etc/mercurial/hgrc`::
     Per-installation configuration files, searched for in the
     directory where Mercurial is installed. `<install-root>` is the
@@ -32,7 +32,7 b' given below, settings from later paths o'
     in `/shared/tools/etc/mercurial/hgrc`. Options in these files apply
     to all Mercurial commands executed by any user in any directory.
 
-(Unix) `/etc/mercurial/hgrc.d/\*.rc`::
+(Unix) `/etc/mercurial/hgrc.d/*.rc`::
 (Unix) `/etc/mercurial/hgrc`::
     Per-system configuration files, for the system on which Mercurial
     is running. Options in these files apply to all Mercurial commands
@@ -48,7 +48,7 b' given below, settings from later paths o'
     which Mercurial is running. Options in these files apply to all
     Mercurial commands executed by any user in any directory. Registry
     keys contain PATH-like strings, every part of which must reference
-    a `Mercurial.ini` file or be a directory where `\*.rc` files will be
+    a `Mercurial.ini` file or be a directory where `*.rc` files will be
     read.
 
 (Unix) `$HOME/.hgrc`::
@@ -144,9 +144,9 b' Example:'
 Supported arguments:
 
   prefix;;
-    Either "`\*`" or a URI prefix with or without the scheme part. The
+    Either "++\*++" or a URI prefix with or without the scheme part. The
     authentication entry with the longest matching prefix is used
-    (where "`\*`" matches everything and counts as a match of length 1).
+    (where "++*++" matches everything and counts as a match of length 1).
     If the prefix doesn't include a scheme, the match is performed
     against the URI with its scheme stripped as well, and the schemes
     argument, q.v., is then subsequently consulted.
@@ -176,8 +176,8 b' decode/encode::'
 Filters consist of a filter pattern followed by a filter command.
 Filter patterns are globs by default, rooted at the repository root.
 For example, to match any file ending in "`.txt`" in the root
-directory only, use the pattern "`\*.txt`". To match any file ending in
-"`.c`" anywhere in the repository, use the pattern "`\*\*.c`".
+directory only, use the pattern "++\*.txt++". To match any file ending in
+"`.c`" anywhere in the repository, use the pattern "++**.c++".
 
 The filter command can start with a specifier, either "pipe:" or
 "tempfile:". If no specifier is given, "pipe:" is used by default.
@@ -667,7 +667,7 b' trusted::'
 --
 This section specifies what users and groups are trusted. The
 current user is always trusted. To trust everybody, list a user or a
-group with name "`\*`".
+group with name "`*`".
 
 users;;
   Comma-separated list of trusted users.
@@ -736,10 +736,10 b' merge-tools section.'
     Warn if a `.hg/hgrc` file is ignored due to not being owned by a
     trusted user or group. True or False. Default is True.
   slash;;
-    Display paths using a slash ("/") as the path separator. This only
+    Display paths using a slash ("++/++") as the path separator. This only
     makes a difference on systems where the default path separator is
     not the slash character (e.g. Windows uses the backslash character
-    ("\")).
+    ("++\++")).
     Default is False.
   ssh;;
     command to use for SSH connections. Default is 'ssh'.
@@ -784,7 +784,7 b' web::'
     Whether to allow pulling from the repository. Default is true.
   allow_push;;
     Whether to allow pushing to the repository. If empty or not set,
-    push is not allowed. If the special value "`\*`", any remote user can
+    push is not allowed. If the special value "`*`", any remote user can
     push, including unauthenticated users. Otherwise, the remote user
     must have been authenticated, and the authenticated user name must
     be present in this list (separated by whitespace or ","). The
@@ -797,7 +797,7 b' web::'
     user is unauthenticated or not present in the list (separated by
     whitespace or ","), then access is denied for the user. If the
     list is empty or not set, then access is permitted to all users by
-    default. Setting allow_read to the special value "`\*`" is equivalent
+    default. Setting allow_read to the special value "`*`" is equivalent
     to it not being set (i.e. access is permitted to all users). The
     contents of the allow_read list are examined after the deny_read
     list.
@@ -813,7 +813,7 b' web::'
     Defaults to ui.username or `$EMAIL` or "unknown" if unset or empty.
   deny_push;;
     Whether to deny pushing to the repository. If empty or not set,
-    push is not denied. If the special value "`\*`", all remote users are
+    push is not denied. If the special value "`*`", all remote users are
     denied push. Otherwise, unauthenticated users are all denied, and
     any authenticated user name present in this list (separated by
     whitespace or ",") is also denied. The contents of the deny_push
@@ -823,7 +823,7 b' web::'
     not empty, unauthenticated users are all denied, and any
     authenticated user name present in this list (separated by
     whitespace or ",") is also denied access to the repository. If set
-    to the special value "`\*`", all remote users are denied access
+    to the special value "`*`", all remote users are denied access
     (rarely needed ;). If deny_read is empty or not set, the
     determination of repository access depends on the presence and
     content of the allow_read list (see description). If both