Single-file decoder script can now (optionally) create an encoder

To complement the single-file decoder a new script was added to create an amalgamated single-file of all of the Zstd source, along with examples and (simple) tests.

lib/compress/huf_compress.c

@@ -41,7 +41,9 @@
 #define HUF_isError ERR_isError
 #define HUF_STATIC_ASSERT(c) DEBUG_STATIC_ASSERT(c)   /* use only *after* variable declarations */
 #define CHECK_V_F(e, f) size_t const e = f; if (ERR_isError(e)) return e
+#ifndef CHECK_F
 #define CHECK_F(f)   { CHECK_V_F(_var_err__, f); }
+#endif
 
 
 /* **************************************************************