Produce direct calls instead of alias to linkonce_odr functions.

This is a small optimization on linux, but should help more on windows
where msvc only outputs one destructor if there would be two identical ones.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@194095 91177308-0d34-0410-b5e6-96231b3b80d8
With this patch -Wwrite-strings is still implemented with the terrible
hack of passing -fconst-strings to -cc1, but at least the driver uses
the regular warning checking code path.

Since we don't support a warning that is DefaultIgnore in one language
but not in another, this patch creates a dummy C only warning in the same
group as the existing one to get the desired effect.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@194097 91177308-0d34-0410-b5e6-96231b3b80d8