Error on more illegal kernel argument types for OpenCL

bool, half, pointers and structs / unions containing any
of these are not allowed. Does not yet reject size_t and
related integer types that are also disallowed.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@186908 91177308-0d34-0410-b5e6-96231b3b80d8