Bug 695171. Make our operator new throw std::bad_alloc. r=cjones

If new doesn't throw bad_alloc the compiler emits a null check after to avoid
calling the constructor. http://llvm.org/bugs/show_bug.cgi?id=10895

Adding throw(std::bad_alloc) shaves 57KB of .text off a gcc mac build and 61KB off
a clang build.

--HG--
extra : rebase_source : 098c1f5df472bcc572b812fe5d4f12c8eadf14d2

memory/mozalloc/mozalloc.h

@@ -214,15 +214,13 @@ MOZALLOC_EXPORT void* moz_valloc(size_t size)
  * to suppress build warning spam (bug 578546).
  */
 #define MOZALLOC_THROW_IF_HAS_EXCEPTIONS /**/
+#define MOZALLOC_THROW_BAD_ALLOC_IF_HAS_EXCEPTIONS
 #else
 #define MOZALLOC_THROW_IF_HAS_EXCEPTIONS throw()
+#define MOZALLOC_THROW_BAD_ALLOC_IF_HAS_EXCEPTIONS throw(std::bad_alloc)
 #endif
 
-#ifdef MOZ_CPP_EXCEPTIONS
-#define MOZALLOC_THROW_BAD_ALLOC throw(std::bad_alloc)
-#else
-#define MOZALLOC_THROW_BAD_ALLOC MOZALLOC_THROW_IF_HAS_EXCEPTIONS
-#endif
+#define MOZALLOC_THROW_BAD_ALLOC MOZALLOC_THROW_BAD_ALLOC_IF_HAS_EXCEPTIONS
 
 MOZALLOC_EXPORT_NEW MOZALLOC_INLINE
 void* operator new(size_t size) MOZALLOC_THROW_BAD_ALLOC