This was, we also avoid Visual Studio compiler warnings C4828 as that sign is
not favored when /utf-8 is enabled, which is the norm nowadays as Visual Studio
2015 or later is required to build harfbuzz nowadays.
This makes it possible to include all .cc files into build, even if not
building CoreText, Uniscribe, etc.
This was mostly to help custom builders. But also means that we can
include all files in our own build system. Not sure if we should.
Definitely simplifies things, but slightly only.
Chun-wei Fan
Behdad Esfahbod
Ebrahim Byagowi