Convert EOL characters
Move private data structure away from public header
Initialize all variables, move variables declaration

Most of variables now declared on first use (as we use C99)
Enforce checking of compiler to be C99 compatible

Also add clang to list of working compilers
Extra space after asterisk character
Proper error handling in lz4stream_write
Proper formatting in lz4stream_close
Add xxhash copyright info
Only lz4stream_* symbols should be exported from .so
Proper "include guards"
Remove extra linefeed
Update changelog