Caf_stop_numeric always exited with code 0, which is wrong.  It shall
behave like regular stop.  Add reporting exceptions to caf's stop
handlers.  For this the existing library routine had to be exported.

libgfortran/ChangeLog:

	PR fortran/57598

	* caf/single.c (_gfortran_caf_stop_numeric): Report exceptions
	on stop. And fix send_by_ref.
	(_gfortran_caf_stop_str): Same.
	(_gfortran_caf_error_stop_str): Same.
	(_gfortran_caf_error_stop): Same.
	* gfortran.map: Add report_exception for export.
	* libgfortran.h (report_exception): Add to internal export.
	* runtime/stop.c (report_exception): Same.