Change -O4 to -O3 -flto on OSX for new clang (should work with older one too)

make-mac.mk

@@ -23,7 +23,7 @@ endif
 #DEFS+=-DZT_TRACE -DZT_LOG_STDOUT 
 
 # Uncomment for a release optimized universal binary build
-CFLAGS=-arch i386 -arch x86_64 -Wall -O4 -fstack-protector -pthread -mmacosx-version-min=10.6 -DNDEBUG -Wno-unused-private-field $(INCLUDES) $(DEFS)
+CFLAGS=-arch i386 -arch x86_64 -Wall -O3 -flto -fvectorize -fstack-protector -pthread -mmacosx-version-min=10.6 -DNDEBUG -Wno-unused-private-field $(INCLUDES) $(DEFS)
 STRIP=strip
 
 # Uncomment for a debug build