Enable intel_ocl_bicc for x86_64 target only. Remove fix from 171969 that enabled this extension for multiple targets.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172052 91177308-0d34-0410-b5e6-96231b3b80d8
r172047 lacked a test (due to incomplete OpenCL support in clang). Use a modified
version of a test by Joey Gouly to use attributes to materialise the unsupported
types and test vector shifts.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172053 91177308-0d34-0410-b5e6-96231b3b80d8