[win] Fix Cygwin build

https://github.com/behdad/harfbuzz/commit/db308280488c2ee11ba865a9922eb6a0c1abeef3#commitcomment-7077778
Disallow changing settings on immutable face

Ouch!
Fix test runner under Windows
0.9.33
Give CC to gir-scanner

From:
https://github.com/Alexpux/MINGW-packages/blob/master/mingw-w64-harfbuzz/0001-give-cc-to-gir-scanner.all.patch
[indic] Handle old-spec Malayalam reordering with final Halant

See comment.

Micro-tests added.
add function to compare two buffers
[compare-shapers] implement the hb-compare-shapers tool
[compare-shapers] add perf stats
Merge branch 'new-compare-shapers' of https://github.com/jfkthame/harfbuzz into new-compare-shapers after rebasing onto upstream/master