Add MS Mangling for OpenCL Pipe types, add mangling test.

SPIRV2.0 Spec only specifies Linux mangling, however our downstream has
use for a Windows mangling for these types.

Unfortunately, the SPIRV
spec specifies a single mangling for all pipe types, despite clang
allowing overloading on these types.  Because of this, this patch
chooses to mangle the read/writability and element type for the windows
mangling.

The windows manglings in the test all demangle according to demangler:
"void __cdecl test1(struct __clang::ocl_pipe<int,1>)
"void __cdecl test2(struct __clang::ocl_pipe<float,0>)
"void __cdecl test2(struct __clang::ocl_pipe<int,1>)
"void __cdecl test3(struct __clang::ocl_pipe<int const,1>)
"void __cdecl test4(struct __clang::ocl_pipe<union
__clang::__vector<unsigned char,3>,1>)
"void __cdecl test5(struct __clang::ocl_pipe<union
__clang::__vector<int,4>,1>)
"void __cdecl test_reserved_read_pipe(struct __clang::_ASCLglobal<struct
Person > * __ptr64,struct __clang::ocl_pipe<struct Person,1>)

Differential Revision: https://reviews.llvm.org/D75685