Support struct arguments with stdarg.h

- add __builtin_va_arg_types to check how arguments were passed
- move most code of stdarg into libtcc1.c
- remove __builtin_malloc and __builtin_free
- add a test case based on the bug report
  (http://www.mail-archive.com/tinycc-devel@nongnu.org/msg03036.html)

tcctok.h

@@ -123,10 +123,7 @@
      DEF(TOK_builtin_constant_p, "__builtin_constant_p")
      DEF(TOK_builtin_frame_address, "__builtin_frame_address")
 #ifdef TCC_TARGET_X86_64
-     DEF(TOK_builtin_malloc, "__builtin_malloc")
-     DEF(TOK_builtin_free, "__builtin_free")
-     DEF(TOK_malloc, "malloc")
-     DEF(TOK_free, "free")
+     DEF(TOK_builtin_va_arg_types, "__builtin_va_arg_types")
 #endif
      DEF(TOK_REGPARM1, "regparm")
      DEF(TOK_REGPARM2, "__regparm__")
@@ -231,10 +228,8 @@
      DEF(TOK___bound_local_new, "__bound_local_new")
      DEF(TOK___bound_local_delete, "__bound_local_delete")
 #ifdef TCC_TARGET_PE
-#ifndef TCC_TARGET_X86_64
      DEF(TOK_malloc, "malloc")
      DEF(TOK_free, "free")
-#endif
      DEF(TOK_realloc, "realloc")
      DEF(TOK_memalign, "memalign")
      DEF(TOK_calloc, "calloc")