Enable to select encoding in hgrc web section

This patch provides character encoding setting in each repository. After this
patch, You can use multi encoding repositories with one mercurial server.

doc/hgrc.5.txt

@@ -551,6 +551,9 b' web::'
     Which template map style to use.
   templates;;
     Where to find the HTML templates. Default is install path.
+  encoding;;
+    Character encoding name.
+    Example: "UTF-8"
 
 
 AUTHOR

mercurial/hgweb/hgweb_mod.py

@@ -103,6 +103,7 b' class hgweb(object):'
             self.maxshortchanges = int(self.config("web", "maxshortchanges", 60))
             self.maxfiles = int(self.config("web", "maxfiles", 10))
             self.allowpull = self.configbool("web", "allowpull", True)
+            self.encoding = self.config("web", "encoding", util._encoding)
 
     def archivelist(self, nodeid):
         allowed = self.configlist("web", "allow_archive")
@@ -655,7 +656,7 b' class hgweb(object):'
     def run_wsgi(self, req):
         def header(**map):
             header_file = cStringIO.StringIO(
-                ''.join(self.t("header", encoding=util._encoding, **map)))
+                ''.join(self.t("header", encoding=self.encoding, **map)))
             msg = mimetools.Message(header_file, 0)
             req.header(msg.items())
             yield header_file.read()