* and #pragma pop_macro("macro_name")

* give warning if pragma is unknown for tcc
    * don't free asm_label in sym_free(),
      it's a job of the asm_free_labels().

    The above pragmas are used in the mingw headers.
    Thise pragmas are implemented in gcc-4.5+ and current
    clang.

tcc.h

@@ -326,6 +326,7 @@
 typedef struct TokenSym {
     struct TokenSym *hash_next;
     struct Sym *sym_define; /* direct pointer to define */
+    struct Sym *sym_define_stack; /* direct pointer to a push_macro stack */
     struct Sym *sym_label; /* direct pointer to label */
     struct Sym *sym_struct; /* direct pointer to structure */
     struct Sym *sym_identifier; /* direct pointer to identifier */