[flang] # This is a combination of 2 commits.

# This is the 1st commit message:

Changes to disallow image control statements in DO CONCURRENT

Most of these changes were already implemented.  The last remaining part was to check for calls to move_alloc with coarray arguments.  This set of changes implements that.  I also bundled other changes.  Specifically:

All of the code to detect image control statements was moved from check-do.cc to tools.cc so that it could be used by other semantic checking functions.

I added location information to the error messages for all DO semantics checks to highlight either the DO loop associated with the error or other relevant source locations.

I cleaned up the error messages associated with DO semantics so that they have more consistent grammar and punctuation.

I eliminated redundant checks for IEEE_GET_FLAG and IEEE_HALTING_MODE.

I removed the redundant test doconcurrent08.f90.

Responses to pull request comments

I changed the interface to determine whether a statement is an image control
statement to use an ExecutableConstruct as its input.  Since
ExecutableConstruct contains types that do not have source location information
(ChangeTeamConstruct and CriticalConstruct), I also created a function to get
the source location of an ExecutableConstruct.  Also, some ExecutableConstructs
are image control statements because they reference coarrays.  I wanted to tell
users that the reason that an ALLOCATE statement (for example) is an image
control statement because it references a coarray.  To make this happen, I
added another function to return a message for image control statements that
reference coarrays.

I also cleaned up the references to the standard in comments in check-do.cc to
briefly describe the contents of those constraints.

I also added messages that refer to the enclosing DO CONCURRENT statement for
error messages where appropriate.

Responses to pull request comments

The biggest change was to redo the implementation of "IsImageControlStmt()" to
use a custom visitor that strips off the "common::Indirection<...>" prefix of
most of the image control statement types and also takes advantage of
"common::HasMember<...>" to determine if a variant contains a specific type.

Spelling error.

# This is the commit message flang-compiler/f18#2:

More refactoring in response to comments on the pull request.

Original-commit: flang-compiler/f18@3f0a0155b3fc3ae8bd81780c1254e235dc272b77
Reviewed-on: https://github.com/flang-compiler/f18/pull/780