commands: 'hg bookmark NAME' should work even with ui.strict=True

Before this patch, enabling strict command processing (ui.strict=True)
meant that 'hg bookmark NAME', as referenced several places in the
documentation, would not work. This adds 'bookmark' as an explicit alias
to 'bookmarks'.

mercurial/commands.py

@@ -758,7 +758,7 b' def bisect(ui, repo, rev=None, extra=Non'
             cmdutil.bailifchanged(repo)
             return hg.clean(repo, node)
 
-@command('bookmarks',
+@command('bookmarks|bookmark',
     [('f', 'force', False, _('force')),
     ('r', 'rev', '', _('revision'), _('REV')),
     ('d', 'delete', False, _('delete a given bookmark')),

tests/test-bookmarks.t

@@ -40,9 +40,9 b' look up bookmark'
   summary:     0
   
 
-second bookmark for rev 0
+second bookmark for rev 0, command should work even with ui.strict on
 
-  $ hg bookmark X2
+  $ hg --config ui.strict=1 bookmark X2
 
 bookmark rev -1 again