Merge pull request #63 from eileencodes/fix-undeclared-function-rb_mmtk_enabled_p

Fix undeclared function `rb_mmtk_enabled_p` when compiling

Author: wks

error.c

@@ -1070,7 +1070,7 @@ rb_bug_for_fatal_signal(ruby_sighandler_t default_sighandler, int sig, const voi
     const char *file = NULL;
     int line = 0;
 
-#ifdef USE_MMTK
+#if USE_MMTK
     // When using MMTk, this function may be called from GC worker threads,
     // in which case there will not be a Ruby execution context.
     if (rb_current_execution_context(!rb_mmtk_enabled_p())) {

gc.c

@@ -10070,7 +10070,7 @@ rb_gc_prepare_heap(void)
 static int
 gc_is_moveable_obj(rb_objspace_t *objspace, VALUE obj)
 {
-#ifdef USE_MMTK
+#if USE_MMTK
     if (rb_mmtk_enabled_p()) {
         rb_bug("Function %s should not be called when MMTk is enabled.", RUBY_FUNCTION_NAME_STRING);
     }