revset: get revision number of each node from target namespaces

Before this patch, revset predicate "named()" uses each nodes gotten
from target namespaces directly.

This causes problems below:

  - combination of other predicates doesn't work correctly, because
    they assume that revisions are listed up in number

  - "hg log" doesn't show any revisions for "named()" result, because:

    - "changeset_printer" stores formatted output for each revisions
      into dict with revision number (= ctx.rev()) as a key of them

    - "changeset_printer.flush(rev)" writes stored output for
      the specified revision, but

    - "commands.log" invokes it with the node, gotten from "named()"

  - "hg debugrevspec" shows nodes (= may be binary) directly

Difference between revset predicate "tag()" and "named('tags')" in
tests is fixed in subsequent patch.

mercurial/revset.py

@@ -1277,7 +1277,7 b' def named(repo, subset, x):'
     names = set()
     for ns in namespaces:
         for name in ns.listnames(repo):
-            names.update(ns.nodes(repo, name))
+            names.update(repo[n].rev() for n in ns.nodes(repo, name))
 
     names -= set([node.nullrev])
     return subset & names

tests/test-revset.t

@@ -787,6 +787,12 b' we can use patterns when searching for t'
   $ log 'present(named("unknown"))'
   $ log 'present(named("re:unknown"))'
 
+  $ log 'tag()'
+  6
+  $ log 'named("tags")'
+  6
+  9
+
 issue2437
 
   $ log '3 and p1(5)'