libstdc++: Define _GLIBCXX_USE_BUILTIN_TRAIT
This patch defines _GLIBCXX_USE_BUILTIN_TRAIT macro, which will be used
as a flag to toggle the use of built-in traits in the type_traits header
through _GLIBCXX_DO_NOT_USE_BUILTIN_TRAITS macro, without needing to modify
the source code.
libstdc++-v3/ChangeLog:
* include/bits/c++config (_GLIBCXX_HAS_BUILTIN): Do not undef.
(_GLIBCXX_USE_BUILTIN_TRAIT): Define.
Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
Reviewed-by: Patrick Palka <ppalka@redhat.com>
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>