MUST_USE_RESULT -> CERES_MUST_USE_RESULT

Change-Id: I23dfde2e699b37840a192fa082e932f5a96dd4a9

include/ceres/internal/macros.h

diff --git a/include/ceres/internal/macros.h b/include/ceres/internal/macros.h
index 388cf30..1ed55be 100644
--- a/include/ceres/internal/macros.h
+++ b/include/ceres/internal/macros.h
@@ -145,12 +145,11 @@
 //
 //   Sprocket* AllocateSprocket() MUST_USE_RESULT;
 //
-#undef MUST_USE_RESULT
 #if (__GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)) \
   && !defined(COMPILER_ICC)
-#define MUST_USE_RESULT __attribute__ ((warn_unused_result))
+#define CERES_MUST_USE_RESULT __attribute__ ((warn_unused_result))
 #else
-#define MUST_USE_RESULT
+#define CERES_MUST_USE_RESULT
 #endif
 
 // Platform independent macros to get aligned memory allocations.