setup.py: Add 'mercurial' as include dir for the inotify compiler.

This patch adds access to util.h for the inotify C module by adding the
"mercurial" directory as an include dir, enabling access to the macros defined
in util.h.

setup.py

@@ -286,7 +286,8 b" if sys.platform == 'linux2' and os.uname"
     cc = new_compiler()
     if hasfunction(cc, 'inotify_add_watch'):
         inotify = Extension('hgext.inotify.linux._inotify',
-                            ['hgext/inotify/linux/_inotify.c'])
+                            ['hgext/inotify/linux/_inotify.c'],
+                            ['mercurial'])
         inotify.optional = True
         extmodules.append(inotify)
         packages.extend(['hgext.inotify', 'hgext.inotify.linux'])