churn and stats commands merged

Eliminate normpath from foldmap calls. Normcase already takes care of upper/lower case and /->\ conversions. What's left for normpath is folding of a/../a sequences but this should be either done consistently on both non-folding and folding code path or not at all, otherwise we are introducing inconsistent behavior between the two that has nothing to do with case folding. Second argument against it - normpath being pure Python function is very slow - as much as 50% of time is spend just inside normpath call on my repository.

issue 1286: dirstat regression on case folding systems This patch fixes regression reported in 1286 that causes util.fspath to be called for every file not in current manifest - including ignored files. The regression is quite severe - the time for simple hg st goes from 5s to 1m38s on one of my source trees - which basically renders mercurial useless.