PR fortran/31189

	PR fortran/31189

	* runtime/backtrace.c (show_backtrace): Skip _gfortrani_handler
	when displaying backtrace.
	* runtime/compile_options.c: Include <signal.h>.
	(handler): New function.
	(set_options): Set signal handlers for backtrace.
	* libgfortran.h (handler): Add prototype.

	* invoke.texi (-fbacktrace): Document the new behaviour.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@127364 138bc75d-0d04-0410-961f-82ee72b054a4