templater: look for mapfiles in template paths

This will allow %include statements to search the default template
paths in addition to the directory where the %including file is.

mercurial/templater.py

@@ -743,7 +743,7 b' class templater(object):'
             raise util.Abort(_("style '%s' not found") % mapfile,
                              hint=_("available styles: %s") % stylelist())
 
-        conf = config.config()
+        conf = config.config(includepaths=templatepaths())
         conf.read(mapfile)
 
         for key, val in conf[''].items():