ninja: Stop lower-casing outputs on case-insensitive file systems.

ninja: Stop lower-casing outputs on case-insensitive file systems.

This was added to fix a problem with file renames that rename a file only
in captialization (https://chromiumcodereview.appspot.com/10907140).  Now
that we use depsmode (which reads deps from a flat text file instead of
doing a lookup for a depsfile on the file system, and which always does
so case-sensitively), this is no longer necessary.  The test we added
when we added this hack still passes.

R=scottmg@chromium.org

Committed: https://code.google.com/p/gyp/source/detail?r=1712

[scottmg, 2013-09-03 21:27:58]

I kind of liked the lowercase names, but I guess we should stick to provided
case. I do vaguely worry this might be hiding some other issues on Windows, but
as that's just superstition, lgtm.

[Nico, 2013-09-04 00:30:32]

Committed patchset #1 manually as r1712 (presubmit successful).