util: add normcase spec and fallback
These will be used in upcoming patches to efficiently create a dirstate
foldmap.
--- a/mercurial/util.py Fri Apr 03 22:44:25 2015 +0200
+++ b/mercurial/util.py Wed Apr 01 00:38:56 2015 -0700
@@ -48,6 +48,8 @@
nlinks = platform.nlinks
normpath = platform.normpath
normcase = platform.normcase
+normcasespec = platform.normcasespec
+normcasefallback = platform.normcasefallback
openhardlinks = platform.openhardlinks
oslink = platform.oslink
parsepatchoutput = platform.parsepatchoutput