[gtk-doc] Initial setup

Initial setup of gtk-doc. Straight forward setup following the gtk-doc
instructions. Ignore some troublesome types in src/hb-gobject.h. To
build use "./autogen.sh --enable-gtk-doc" then "make". Docs are in
harfbuzz/docs/reference/html/index.html.
[travis] Add graphite2
Add HB_DISABLE_DEPRECATED

That moment that you have to accept that you made API mistakes...
[git.mk] Update
[gtk-doc] Remove tmpl in make maintainer-clean
[check-*] Minor
Fix possible snprintf OOM

https://bugzilla.redhat.com/show_bug.cgi?id=1001645
[gtk-doc] Fix maintainer-clean rule
Minor
Improve check-includes.sh
Separate face source code from font

Makes documentation / introspection easier.
Add hb-deprecated.h, and rename a couple enum values

Add deprecated alias for old name.
[uniscribe] Fixed build with wide chars

https://github.com/blinkseb/harfbuzz/commit/f65dafa4138e1fb4395bf646fa33bb01a86a7e9a
[introspection] Enable gobject-introspection again
[gobject] Flesh out hb-gobject

Move it to new harfbuzz-gobject library.  Implement enums and
boxed types for object-types.  Still have to do boxed types for
value types.
Hookup harfbuzz-gobject to introspection
Turn hb-gobject, and introspection off by default

Also enable bootstrapping without them.
Fix build
Remove gtk-doc.make

It's copied by gtk-docize.
[gtk-doc] Fix build without gobject