highlight: move code from module top-level into extsetup

hgext/highlight/__init__.py

@@ -53,6 +53,7 b' def generate_css(web, req, tmpl):'
     req.respond(common.HTTP_OK, 'text/css')
     return ['/* pygments_style = %s */\n\n' % pg_style, fmter.get_style_defs('')]
 
+def extsetup():
 # monkeypatch in the new version
 extensions.wrapfunction(webcommands, '_filerevision', filerevision_highlight)
 extensions.wrapfunction(webcommands, 'annotate', annotate_highlight)