Modified : Streaming API, using strong types

Added : LZ4_versionNumber(), thanks to Takayuki Matsuoka
Fix : OS-X : library install name, thanks to Clemens Lang
Updated : Makefile : synchronize library version number with lz4.h, thanks to Takayuki Matsuoka
Updated : Makefile : stricter compilation flags
Added : pkg-config, thanks to Zbigniew Jędrzejewski-Szmek (issue 135)
Makefile : lz4-test only test native binaries, as suggested by Michał Górny (issue 136)
Updated : xxHash to r35