Fix SUPPLY_MISSING_INT128_TRAITS

Summary:
The original code `AC_DEFINE([FOLLY_SUPPLY_MISSING_INT128_TRAITS...` resulted in defining the constant FOLLY_FOLLY_SUPPLY_MISSING_INT128_TRAITS in folly-config.h. This patch fix the name of the constant so that the name match with what appear in Traits.h.
Closes https://github.com/facebook/folly/pull/485

Reviewed By: yfeldblum

Differential Revision: D3931349

Pulled By: Orvid

fbshipit-source-id: bd7e7d3580d02134d36706bd5836822135232d26

folly/configure.ac

@@ -171,7 +171,7 @@ static_assert(
       [folly_cv_prog_cc_int128traits=no])
     ])
   if test "$folly_cv_prog_cc_int128traits" = "no"; then
-    AC_DEFINE([FOLLY_SUPPLY_MISSING_INT128_TRAITS], [1], [Define if we need the standard integer traits defined for the type `__int128'.])
+    AC_DEFINE([SUPPLY_MISSING_INT128_TRAITS], [1], [Define if we need the standard integer traits defined for the type `__int128'.])
   fi
 fi