[PowerPC] Add vec_vsx_ld and vec_vsx_st intrinsics

This patch enables the vec_vsx_ld and vec_vsx_st intrinsics for
PowerPC, which provide programmer access to the lxvd2x, lxvw4x,
stxvd2x, and stxvw4x instructions.

New code in altivec.h defines these in terms of new builtins, which
are themselves defined in BuiltinsPPC.def.  The builtins are converted
to LLVM intrinsics in CGBuiltin.cpp.  Additional code is added to
builtins-ppc-vsx.c to verify the correct generation of the intrinsics.

Note that I moved the other VSX builtins so all VSX builtins will be
alphabetical in their own section in BuiltinsPPC.def.

There is a companion patch for LLVM.


git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@221768 91177308-0d34-0410-b5e6-96231b3b80d8
Mark TypeDecls used in explicit destructor calls as referenced.

Fixes PR21221. Patch by Axel Naumann, test by me.


git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@221771 91177308-0d34-0410-b5e6-96231b3b80d8