initial import of brotli 1.0.9.

modern blender wants freetype to have brotli support enabled or it
won't build. fortunately, enabling the decoder support (all it
needs currently) is relatively easy and small (~160k on amd64)
without exposing brotli as a first class citizen is easy, so this
will be linked into xsrc freetype directly.

XXX: pullup-10? or perhaps force -10 to use pkgsrc freetype?

from pkgsrc DESCR:
Brotli is a generic-purpose lossless compression algorithm that compresses data
using a combination of a modern variant of the LZ77 algorithm, Huffman coding
and 2nd order context modeling, with a compression ratio comparable to the best
currently available general-purpose compression methods. It is similar in speed
with deflate but offers more dense compression.