Fixed more warnings

Makefile

@@ -13,7 +13,6 @@ ifeq ($(CC), clang)
 		-Wno-conversion               \
 		-Wno-disabled-macro-expansion \
 		-Wno-padded                   \
-		-Wno-undef \
 		-Wno-format-nonliteral
 
 endif

gmqcc.h

@@ -53,12 +53,16 @@
 #   endif /* !true  */
 #   define false (0)
 #   define true  (1)
+#   ifdef __STDC_VERSION__
 #       if __STDC_VERSION__ < 199901L && __GNUC__ < 3
-        typedef int  _Bool
+            typedef int  bool;
 #       else
             typedef _Bool bool;
 #       endif
-#   endif /* !__cplusplus */
+#   else
+        typedef int bool;
+#   endif /* !__STDC_VERSION__ */
+#endif    /* !__cplusplus      */
 
 /*
  * Of some functions which are generated we want to make sure
@@ -81,7 +85,8 @@
  * like gcc and clang might have an inline attribute we can
  * use if present.
  */
-#if __STDC_VERSION__ < 199901L
+#ifdef __STDC_VERSION__
+#    if __STDC_VERSION__ < 199901L
 #       if defined(__GNUC__) || defined (__CLANG__)
 #           if __GNUC__ < 2
 #               define GMQCC_INLINE
@@ -91,9 +96,12 @@
 #       else
 #           define GMQCC_INLINE
 #       endif
-#else
+#    else
 #       define GMQCC_INLINE inline
-#endif
+#    endif
+#else
+#    define GMQCC_INLINE
+#endif /* !__STDC_VERSION__ */
 
 /*
  * noreturn is present in GCC and clang