Improve ASMA972U messages

This message provides absolutely no useful information whatsoever to
determine the cause of the error. The statement number is totally
useless as there is no indication what the source of that statement
might have been. It could have been open code, a copybook, a macro,
etc. The storage dump of 80 bytes of zeroes is also totally useless.

The message description states truthfully that storage was exhausted
and suggests increasing the SIZE parameter. That might be useful in a
fraction of the cases where this message is produced. But the more
likely cause of this message is some recursion in the assembler input,
such as a macro calling itself.

At the very least, the assembler needs to identify the source of the
statement being processed, i.e. sysin or copy/macro member name, and
the statement number in that source. The message description also needs
to be augmented to suggest the recursion scenario.

It would also be a nice feature to implement a new feature, similar to
ACTR, that could limit the nesting depth of macros. It should be
settable by the user (as is ACTR), but have some reasonable default ,
maybe 25 or so. This could stop unintended recursion before virtual
storage was exhausted and would facilitate diagnosing this type of
program error.