[m-rev.] for review: fix bugs in reporting insts

[Julien Fischer]

On Sat, 5 Feb 2022, Zoltan Somogyi wrote:

> Fix formatting when reporting problem insts.
> 
> compiler/error_msg_inst.m:
>     Fix a bug that caused the suffix that all paths in two predicates
>     were supposed to add at the logical end of the constructed pieces
>     (though it could be followed by some punctuation) to *not* be added
>     to the constructed pieces on some paths. Since with our current approach,
>     the suffix for one inst in a list of insts can be the description
>     of *all the insts following it in the list*, this bug could delete
>     not just punctuation, but entire insts from the output. This did actually
>     happen for the invalid/html text case below.
>
>     Fix a problem that could cause each inst in a list of insts
>     to be indented one more level than the previous inst, which can be
>     very confusing.
>
>     Delete the comma from "instname, which expands to ...". When this output
>     occurs in an argument list, the presence of the comma can make it
>     harder to recognize where one argument ends and the next argument begins.
>
>     Factor out some commonn code.

s/commonn/common/

>
>     Add an XXX noting a problem.
>
>     Fix documentation.

The rest looks fine.

Julien.