Replace ATS/ATSUI with Core Text

Slightly adapted from code by Jjgod Jiang:
https://github.com/jjgod/xetex/commit/26b80b6a946164f4b5b2a565702bc6789a568229
Make it build
Now make it build again on non-Mac
Merge branch 'master' into coretext

Conflicts:
	texk/web2c/xetexdir/XeTeXFontInst_Mac.cpp
	texk/web2c/xetexdir/XeTeX_ext.c
Fix malloc error

malloc: *** error for object 0x104440b18: pointer being freed was not allocated
Fix a thinko

I want the FromCTFont not the wrapper _AAT functions (the later were
giving me 0 glyph indices anyway).
Attempt to restore AAT layout

XeTeX does not crash, but xdvipdfmx does not like the glyph ids it gets.
Fix a crash in loadAATfont with no featString given
Fix a crash in atsufontget1 when accessing non-exist feature key
Fix a crash in atsufontget2 when accessing non-exist feature selector
Don’t build FreeType with old Mac fonts support

A workaround for the HarfBuzz/FreeType build issue for now.
Fix findSelectorByName
Merge branch 'master' into coretext
Attempt to fix wrong glyph id with AAT fonts
Yet another attempt to fix DoAtsuiLayout

Still not quite working yet but better and should not trigger crash on
story-zapfino.tex.

- Better handling when justify == 1 and Core Text failed to provide a
  justified line (returns == NULL).
- Include fontletterspace[f] in node_width calculation.
- node_width(node) should be the x position of second to last glyph
  instead of last glyph + lsDelta. (I wonder how do we take the width
  of last glyph into account.)
Fixup to previous patch
Add the last glyphs advance seems to fix the layout problem
Simplify

fontletterspace[f] is always zero, it does not make any difference
Use CTRunGetTypographicBounds()
Minor