I fixed an assert caused by passing an empty array as the source= argument to
RESHAPE(). In the process, I noticed that there were no tests for RESHAPE(),
so I wrote a test that covers all the description in 16.9.163. In the process,
I made the error messages more consistent and descriptive. I also changed the
test to see if a reference to an intrinsic function was a constant to say that
it is a constant if it's a refererence to an invalid intrinsic. This avoids
emitting multiple messages for the same erroneous source.
Differential Revision: https://reviews.llvm.org/D84904