doc: escape .hg at bol in manpages with make (issue1072)

This works around a bug in old docbook stylesheets.
Remove .*.swp example from hgignore.5.txt.

Diagnosis and workaround thanks to Alexis S. L. Carvalho.

doc/Makefile

@@ -18,7 +18,9 b' hg.1.gendoc.txt: ../mercurial/commands.p'
 	python gendoc.py > $@
 
 %: %.xml
-	xmlto man $*.xml
+	xmlto man $*.xml ; \
+	sed -e 's/^\.hg/\\\&.hg/' $* > $*~ ; \
+	mv $*~ $*
 
 %.xml: %.txt
 	asciidoc -d manpage -b docbook $*.txt

doc/hgignore.5.txt

@@ -68,7 +68,6 b' Here is an example ignore file.'
   *.elc
   *.pyc
   *~
-  .*.swp
 
   # switch to regexp syntax.
   syntax: regexp