This brings various improvements to the current Makefile and intends to help
people to package WOFF2:
* Build and install static and shared libraries for encoder and decoder
* Install public headers
* Generate and install pc files for PkgConfig
* Build the woff2_* programs
* Build the fuzzer archives
* Specify a release version (0.0.1 is hardcoded for now)
* Build using a Brotli version installed on the system, instead of the git
submodule
* Have some CANONICAL_PREFIXES and NOISY_LOGGING configuration options
Frédéric Wang