[flang] Support for image selectors

Summary:
This change implements support for image selectors and image selector
specifications as described in section 9.6.

In check-coarray[.h,cpp] I changed the `Leave()` function for
`parser::ImageSelectorSpec` to take a `parser::ImageSelector`, which
contains a list of image selector specifications.  This allows us to
detect when the same specification is used more than once.  I also added
code to analyze the expressions for the image selector specifications to
expression.cpp and a test for all of the conditions to check at
compile-time.

Note that we do not check at compile-time to see if the value of the
cosubscripts are within the specified cobounds.  We also do not check anything
related to selecting a valid team.  We also do not check that the denotation of
the `stat-variable` is not dependent on the evaluation of an entity in the
same statement.

Reviewers: klausler, tskeith, DavidTruby

Subscribers: llvm-commits

Tags: #llvm, #flang

Differential Revision: https://reviews.llvm.org/D83336

0 files changed, 0 insertions, 0 deletions