Add block splitter to experimental params

lib/compress/zstd_compress_internal.h

@@ -312,6 +312,9 @@ struct ZSTD_CCtx_params_s {
     ZSTD_sequenceFormat_e blockDelimiters;
     int validateSequences;
 
+    /* Block splitting */
+    int splitBlocks;
+
     /* Internal use, for createCCtxParams() and freeCCtxParams() only */
     ZSTD_customMem customMem;
 };  /* typedef'd to ZSTD_CCtx_params within "zstd.h" */