hgmanpage: fix grammar

remove 's's from places where they don't belong
insert the preposition 'in'

doc/hgmanpage.py

@@ -18,11 +18,11 b' systems. The pages are grouped in number'
  7 miscellaneous
  8 system administration
 
-Man pages are written *troff*, a text file formatting system.
+Man pages are written in *troff*, a text file formatting system.
 
 See http://www.tldp.org/HOWTO/Man-Page for a start.
 
-Man pages have no subsection only parts.
+Man pages have no subsections only parts.
 Standard parts
 
   NAME ,
@@ -317,7 +317,7 b' class Translator(nodes.NodeVisitor):'
                     self._cnt = 0
                 self._indent = 2
                 if style == 'arabic':
-                    # indentation depends on number of childrens
+                    # indentation depends on number of children
                     # and start value.
                     self._indent = len(str(len(node.children)))
                     self._indent += len(str(self._cnt)) + 1