Add a test with a range of this_image() intrinsic function
invocations, including a comprehensive set of standard-conforming
keyword and non-keyword arguments with and without optional
arguments present and with argument positions covering all
possible orderings. Also test that several non-conforming
this_image() invocations generate the correct error messages.
Differential Revision: https://reviews.llvm.org/D123331
Damian Rouson