Move asm label functions from tccasm.c to tccgen.c

* Move functions parse_asm_str and asm_label_instr from tccasm.c to
  tccgen.c
* Remove CONFIG_TCC_ASM_LABEL macro as asm label are available on all
  archs.
See:
http://lists.nongnu.org/archive/html/tinycc-devel/2010-09/msg00026.html
for the rationale.

libtcc.c

@@ -72,12 +72,6 @@ ST_DATA void *rt_prog_main;
 #endif /* ALL_IN_ONE */
 
 /********************************************************/
-#ifndef CONFIG_TCC_ASM_LABEL
-ST_FUNC void asm_label_instr(CString *)
-{
-    error("inline asm() not supported");
-}
-#endif
 #ifndef CONFIG_TCC_ASM
 ST_FUNC void asm_instr(void)
 {