completed ZSTDMT streaming compression

completed ZSTDMT streaming compression

Provides the baseline compression API :
size_t ZSTDMT_initCStream(ZSTDMT_CCtx* zcs, int compressionLevel);
size_t ZSTDMT_compressStream(ZSTDMT_CCtx* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
size_t ZSTDMT_flushStream(ZSTDMT_CCtx* zcs, ZSTD_outBuffer* output);
size_t ZSTDMT_endStream(ZSTDMT_CCtx* zcs, ZSTD_outBuffer* output);

Not tested yet