[libcxx] Enable noexcept for GCC 4.6 and greater
Summary:
This patch allows GCC 4.6 and above to use `noexcept` as opposed to
`throw()`.
Is it an ABI safe change to suddenly switch on `noexcept`? I imagine
it must be because it's disabled in w/ clang in C++03 but not C++11.
Reviewers: danalbert, jroelofs, mclow.lists
Subscribers: cfe-commits
Differential Revision: http://reviews.llvm.org/D15516
This should fix errors from gcc 4.6 and higher when compiling llvm-cov
and/or other llvm tools.
Reported by: bdrewery
