CallInfo bit CIST_CLSRET broken in two

Since commit f407b3c4a, it was being used for two distinct (and
incompatible) meanings:
A: Function has TBC variables (now bit CIST_TBC)
B: Interpreter is closing TBC variables (original bit CIST_CLSRET)

B implies A, but A does not imply B.

lstate.h

@@ -235,8 +235,10 @@ struct CallInfo {
 #define CIST_FRESH	cast(l_uint32, CIST_C << 1)
 /* function is closing tbc variables */
 #define CIST_CLSRET	(CIST_FRESH << 1)
+/* function has tbc variables to close */
+#define CIST_TBC	(CIST_CLSRET << 1)
 /* original value of 'allowhook' */
-#define CIST_OAH	(CIST_CLSRET << 1)
+#define CIST_OAH	(CIST_TBC << 1)
 /* call is running a debug hook */
 #define CIST_HOOKED	(CIST_OAH << 1)
 /* doing a yieldable protected call */