[TargetLibraryInfo] Pick new/delete calls by target

There are two sets of new/delete functions, one with Windows/MSVC
mangling and one with Itanium mangling. Mark one set or the other
as unavailable depending on the target.

Split the test malloc-free-delete.ll into three parts: malloc-free.dll
for the C API tests, new-delete-itanium.ll and new-delete-msvc.ll for
the target-specific new/delete tests.

Differential Revision: https://reviews.llvm.org/D110419