Merge pull request #7 from Cyan4973/dev

LZ4 streaming API
Merge pull request #8 from Cyan4973/dev

updated NEWS
Merge pull request #11 from Cyan4973/dev

Dev
Restored : lz4 compression function using externally allocated memory for state
Added : pkg-config (issue 135)
Merge branch 'dev' of https://github.com/Cyan4973/lz4 into dev
Added : LZ4_versionNumber(), thanks to Takayuki Matsuoka
Makefile : some corrections suggested by Michał Górny (issue 136)