Bugzilla bug 14357

Merge SPIR64 target from trunk - the 64bit counterpart of SPIR.

The new OpenCL SPIR extension spec will define separate SPIR for 32 and 64 bit architectures.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_32@168092 91177308-0d34-0410-b5e6-96231b3b80d8