introduced strategy btultra2

note : not yet applied on any compression level

lib/zstd.h

@@ -494,7 +494,8 @@ typedef enum { ZSTD_fast=1,
                ZSTD_lazy2=5,
                ZSTD_btlazy2=6,
                ZSTD_btopt=7,
-               ZSTD_btultra=8
+               ZSTD_btultra=8,
+               ZSTD_btultra2=9
                /* note : new strategies might be added in the future.
                          Only the order (from fast to strong) is guaranteed, not the exact position.
                          new strategy names might be introduced, pushing the maximum number upward */