Revision of stackless implementation

- more organized handling of 'nCcalls'
- comments
- deprecation of 'setcstacklimit'

lparser.c

@@ -489,11 +489,7 @@ static void adjust_assign (LexState *ls, int nvars, int nexps, expdesc *e) {
 }
 
 
-static void enterlevel (LexState *ls) {
-  lua_State *L = ls->L;
-  L->nCcalls++;
-  checklimit(ls->fs, getCcalls(L), LUAI_MAXCCALLS, "C levels");
-}
+#define enterlevel(ls)	luaE_incCstack(ls->L)
 
 
 #define leavelevel(ls) ((ls)->L->nCcalls--)