Reduce streaming decompression memory by 128KB

The split literals buffer patch increased streaming decompression memory
by 64KB (shrunk lit buffer from 128KB to 64KB, and added 128KB). This
patch removes the added 128KB buffer, because it isn't necessary.

The buffer was there because the literals compression code didn't know
the true `blockSizeMax` of the frame, and always put split literals so
they ended 128KB - 32 from the beginning of the block. Instead, we can
pass down the true `blockSizeMax` and ensure that the split literals
end up at `blockSizeMax - 32` from the beginning of the block. We
already reserve a full `blockSizeMax` bytes in streaming mode, so we
won't be overwriting the extDict window.

lib/decompress/zstd_decompress_internal.h

@@ -153,6 +153,7 @@ struct ZSTD_DCtx_s
     size_t litSize;
     size_t rleSize;
     size_t staticSize;
+    int isFrameDecompression;
 #if DYNAMIC_BMI2 != 0
     int bmi2;                     /* == 1 if the CPU supports BMI2 and 0 otherwise. CPU support is determined dynamically once per context lifetime. */
 #endif