Update (#630)

 * merge {dec|enc}/port.h into common/platform.h
 * fix one-shot q=10 1-byte input compression
 * fix some unprefixed definitions
 * make hashers host-endianness-independent
 * extract enc/params.h from enc/quality.h
 * fix API documentation / typos
 * improve `BrotliEncoderMaxCompressedSize`