Tweaks to create a single-file decoder

The CHECK_F macros differ slightly (but eventually do the same thing). Older GCC needs to fallback on the old-style pragma optimisation flags.

lib/decompress/huf_decompress.c

@@ -61,7 +61,9 @@
 *  Error Management
 ****************************************************************/
 #define HUF_isError ERR_isError
+#ifndef CHECK_F
 #define CHECK_F(f) { size_t const err_ = (f); if (HUF_isError(err_)) return err_; }
+#endif
 
 
 /* **************************************************************