[util] Add a function to reverse delete cbuf stacks

I'm not 100% sure this is the best fix for the issue, but the way the
cbuf interpreter stack works (especially in the console code) meant that
the stack was built in the order opposite to how it could be safely
deleted with the existing function. Yeah, more leaks :P

include/QF/cbuf.h

@@ -92,6 +92,7 @@ cbuf_t * Cbuf_New (cbuf_interpreter_t *interp);
 
 void Cbuf_Delete (cbuf_t *cbuf);
 void Cbuf_DeleteStack (cbuf_t *stack);
+void Cbuf_DeleteStackReverse (cbuf_t *stack);
 void Cbuf_Reset (cbuf_t *cbuf);
 cbuf_t *Cbuf_PushStack (cbuf_interpreter_t *interp);
 void Cbuf_AddText (cbuf_t *cbuf, const char *text);

libs/util/cbuf.c

@@ -123,6 +123,17 @@ Cbuf_DeleteStack (cbuf_t *stack)
 	}
 }
 
+VISIBLE void
+Cbuf_DeleteStackReverse (cbuf_t *stack)
+{
+	cbuf_t		*next;
+
+	for (; stack; stack = next) {
+		next = stack->up;
+		Cbuf_Delete (stack);
+	}
+}
+
 void
 Cbuf_Reset (cbuf_t *cbuf)
 {

ruamoko/qwaq/builtins/main.c

@@ -486,7 +486,7 @@ main (int argc, char **argv)
 		free (thread_data.a[i]);
 	}
 	DARRAY_CLEAR (&thread_data);
-	Cbuf_Delete (qwaq_cbuf);
+	Cbuf_DeleteStackReverse (qwaq_cbuf);
 	Sys_Shutdown ();
 	return ret;
 }