normalize xcam_common/utils/defs headers

 force all c++ headers to include xcam_utils.h
diff --git a/xcore/xcam_utils.h b/xcore/xcam_utils.h
index c44f621..67de963 100644
--- a/xcore/xcam_utils.h
+++ b/xcore/xcam_utils.h
@@ -21,6 +21,10 @@
 #ifndef XCAM_UTILS_H
 #define XCAM_UTILS_H
 
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
 #include "xcam_common.h"
 
 namespace XCam {