Issue #1729 - Support building/linking against libc++ 9+

Including <cstdlib> must never trigger inclusion of "mozalloc.h", because the
first thing this one does is precisely to include <cstdlib>.

It is now the case that, in libc++ 9 and beyond, <cstdlib> includes <math.h>
which then tries to include <type_traits>, which the STL wrapper intercepts,
trying to load "mozalloc.h". Same problem happens with <limits>.

Fix pulled from: https://bugzilla.mozilla.org/show_bug.cgi?id=1594027.

config/gcc-stl-wrapper.template.h

@@ -32,6 +32,14 @@
 #  define moz_dont_include_mozalloc_for_cstdlib
 #endif
 
+#ifndef moz_dont_include_mozalloc_for_type_traits
+#  define moz_dont_include_mozalloc_for_type_traits
+#endif
+
+#ifndef moz_dont_include_mozalloc_for_limits
+#  define moz_dont_include_mozalloc_for_limits
+#endif
+
 // Include mozalloc after the STL header and all other headers it includes
 // have been preprocessed.
 #if !defined(MOZ_INCLUDE_MOZALLOC_H) && \