Not all the compilers that HarfBuzz is buildable on supports round() and
has the header stdbool.h, so we check for them and define HAVE_ROUND and
HAVE_STDBOOL_H repsectively in our CFLAGS so that we include them only
when they are found, or use fallback implementations when necessary.

Also include FindPythonInterp earlier as we need PYTHON_EXECUTABLE to be
set for running the tests.

[subset] Drop the same tables by default as fontTools does.

Fixes #873

This makes ArchLinux bots fail, a starting point to #873

[subset] Add a Japanese font to the subset integration tests.

[subset] Drop glyph names from post when subsetting.

[subset] Add vmtx subsetting.

So I can make a release.

BASE table API will go into hb-ot-layout.h.

Was totally b0rked. Ouch!

Fixes https://github.com/harfbuzz/harfbuzz/issues/863

In preparation to fix https://github.com/harfbuzz/harfbuzz/issues/863

Binary operations are sets are completely broken. Ouch.

* Implemented a bsearch on get_base_glyph_record
* Made get_color_record_argb actually work