overlapSimpleBitmap is a new field in the transformed glyf table (https://www.w3.org/TR/WOFF2/#glyf_table_format). It allows the overlap simple flag set on glyphs in the original font to be saved into the woff2 encoding.
This is a first step to make WOFF2 a shared library. Public headers are moved
in their own directory to make the public API clearer. This is similar to
the c/include/brotli/ directory in Brotli. "using" commands are also removed
from the public headers, so that callers won't have unexpected side effect
when including the files.
There is only a single data stream for all the compressed tables, but
the code was originally written for separately compressed tables then
retrofitted, so this is an attempt to streamline it a bit.
Garret Rieger