Add an explicit test of the auto-upgrade functionality for the new

intrinsic syntax.

Now that this is explicitly covered, I plan to upgrade the existing test
suite to use an explicit immediate. Note that I plan to specify 'true'
in most places rather than the auto-upgraded value as that is the far
more common value to end up here as that is the value coming from GCC's
builtins. The only place I'm likely to put a 'false' in is when testing
x86 which actually has different instructions for the two variants.

llvm-svn: 146369