[libc++] Remove C++03 variadics in shared_ptr (v2)

    Summary: In my last patch (D67675) I forgot a few variadics. This patch removes the remaining make_shared and allocate_shared C++03 variadics.

    Reviewers: ldionne, EricWF, mclow.lists

    Subscribers: christof, dexonsmith, libcxx-commits

    Tags: #libc

    Differential Revision: https://reviews.llvm.org/D68000

llvm-svn: 373971