analyzer: log the stashing of named constants [PR107711]

PR analyzer/107711 seems to be a bug in how named constants are looked up
by the analyzer in the C frontend.

To help debug this, this patch extends -fdump-analyzer and
-fdump-analyzer-stderr so that they dump this part of the analyzer's
startup.

gcc/analyzer/ChangeLog:
	PR analyzer/107711
	* analyzer-language.cc: Include "diagnostic.h".
	(maybe_stash_named_constant): Add logger param and use it to log
	the name being looked up, and the result.
	(stash_named_constants): New, splitting out from...
	(on_finish_translation_unit): ...this function.  Call
	get_or_create_logfile and use the result to create a logger
	instance, passing it to stash_named_constants.
	* analyzer.h (get_or_create_any_logfile): New decl.
	* engine.cc (dump_fout, owns_dump_fout): New globals, split out
	from run_checkers.
	(get_or_create_any_logfile): New function, split out from...
	(run_checkers): ...here, so that the logfile can be opened by
	on_finish_translation_unit.  Clear the globals when closing the
	dump file.

gcc/testsuite/ChangeLog:
	PR analyzer/107711
	* gcc.dg/analyzer/fdump-analyzer-1.c: New test.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>