64-bit tests now pass (well, nearly).

tcctest1-3 fail, but this appears to be due to bugs in GCC rather than TCC
(from manual inspection of the output).

tcctok.h

@@ -125,7 +125,11 @@
      DEF(TOK_builtin_constant_p, "__builtin_constant_p")
      DEF(TOK_builtin_frame_address, "__builtin_frame_address")
 #ifdef TCC_TARGET_X86_64
+#ifdef TCC_TARGET_PE
+     DEF(TOK_builtin_va_start, "__builtin_va_start")
+#else
      DEF(TOK_builtin_va_arg_types, "__builtin_va_arg_types")
+#endif
 #endif
      DEF(TOK_REGPARM1, "regparm")
      DEF(TOK_REGPARM2, "__regparm__")