As https://github.com/harfbuzz/harfbuzz/pull/1059#issuecomment-397912812 we
like to still work with blobs that harfbuzz itself can't handle directly that are failing sanitization
currently apparently.

This checks if the blob isn't empty and uses `hb_face_count`
to see if the font file passes the simple font file sanitization
so can detect if the input is actually a font and checks also
whether input font-index is out of range.

We were passing the font path directly to freetype so rendering
was broken when we are getting the font from stdin.

This fixes it by using FT_New_Memory_Face instead.

This fixes:
* build/util/hb-view /dev/stdin text < font.ttf
* build/util/hb-view - text < font.ttf
* cat font.ttf | build/util/hb-view - text

but doesn't work on
* cat font.ttf | build/util/hb-view /dev/stdin text

which I will try to fix separately.

A bit brute force and requires all shapers to be known, not just one.

Fixes https://github.com/harfbuzz/harfbuzz/issues/956

Something weird seems to be going on. Just kill it.

Fixes https://github.com/harfbuzz/harfbuzz/issues/888

To signify that unlike rest of library, returns nullptr on failure.

To work around mysterious bug on OS X.

Fixes https://github.com/harfbuzz/harfbuzz/issues/727

tweak test failure output. write to a temp file not stdout. test still fails because expected is not just an identical copy of input

Fixes https://github.com/harfbuzz/harfbuzz/issues/711