Rename some internal templates to avoid conflict with complier
intrinsics. __is_constructible --> __libcpp_is_constructible,
__is_nothrow_constructible --> __libcpp_is_nothrow_constructible, and
__is_nothrow_assignable --> __libcpp_is_nothrow_assignable. No
functionality change.
Pull in r206805 from upstream libc++ trunk (by Marshall Clow):
Use compiler intrinsic __is_constructible if available
This should fix building parts of world with -std=c++11 enabled.
Reported by: Oliver Hartmann <ohartman@zedat.fu-berlin.de>
MFC after: 1 week
4eb40d1e51