Fixes #3: unity_fixture tests don't build. unity.c and...

Fixes #3: unity_fixture tests don't build. unity.c and unity_fixture_malloc_overrides.h neglected to include <stddef.h> even though the reference 'size_t' and 'NULL'.

extras/fixture/src/unity_fixture_malloc_overrides.h

@@ -8,6 +8,8 @@
 #ifndef UNITY_FIXTURE_MALLOC_OVERRIDES_H_
 #define UNITY_FIXTURE_MALLOC_OVERRIDES_H_
 
+#include <stddef.h>
+
 #define malloc  unity_malloc
 #define calloc  unity_calloc
 #define realloc unity_realloc

src/unity.c

@@ -5,6 +5,7 @@
 ============================================================================ */
 
 #include "unity.h"
+#include <stddef.h>
 
 #define UNITY_FAIL_AND_BAIL   { Unity.CurrentTestFailed  = 1; longjmp(Unity.AbortFrame, 1); }
 #define UNITY_IGNORE_AND_BAIL { Unity.CurrentTestIgnored = 1; longjmp(Unity.AbortFrame, 1); }