PR 46686 Implement backtrace with _Unwind_Backtrace from libgcc.

2011-11-09  Janne Blomqvist  <jb@gcc.gnu.org>

	PR fortran/46686
	* configure.ac: Don't check execinfo.h, backtrace,
	backtrace_symbols_fd. Check execve instead of execvp. Call
	GCC_CHECK_UNWIND_GETIPINFO.
	* runtime/backtrace.c: Don't include unused headers, include
	limits.h and unwind.h.
	(CAN_FORK): Check execve instead of execvp.
	(GLIBC_BACKTRACE): Remove.
	(bt_header): Conform to gdb backtrace format.
	(struct bt_state): New struct.
	(trace_function): New function.
	(show_backtrace): Use _Unwind_Backtrace from libgcc instead of
	glibc backtrace functions.
	* Makefile.in: Regenerated.
	* aclocal.m4: Regenerated.
	* config.h.in: Regenerated.
	* configure: Regenerated.

From-SVN: r181209