WindowsX86: long double is x87DoubleExtended on mingw

    Summary:
    long double on x86 mingw is 80bits and is aligned to 16bytes

	Fixes:
    https://llvm.org/bugs/show_bug.cgi?id=24398

    Reviewers: rnk

    Subscribers: cfe-commits

    Differential Revision: http://reviews.llvm.org/D12037

llvm-svn: 245084