Removed raw references to __APPLE__; now just check to see if it is defined.

llvm-svn: 177297
diff --git a/libcxx/src/new.cpp b/libcxx/src/new.cpp
index 3ad593a..b23a516 100644
--- a/libcxx/src/new.cpp
+++ b/libcxx/src/new.cpp
@@ -15,7 +15,7 @@
 #define __has_include(inc) 0
 #endif
 
-#if __APPLE__
+#ifdef __APPLE__
     #include <cxxabi.h>
 
     #ifndef _LIBCPPABI_VERSION