cleanup: Consolidate countof macros.

src/util.js.h

@@ -150,4 +150,11 @@ const char* tf_util_function_to_string(void* function);
 		_a > _b ? _b : _a; \
 	})
 
+/**
+** Get the number of elements in an array.
+** @param a The array.
+** @return The number of array elements.
+*/
+#define tf_countof(a) ((int)(sizeof((a)) / sizeof(*(a))))
+
 /** @} */