* gfortran.h (gfc_option_t): Add flag_backtrace field.
	* lang.opt: Add -fbacktrace option.
	* invoke.texi: Document the new option.
	* trans-decl.c (gfc_build_builtin_function_decls): Add new
	option to the call to set_std.
	* options.c (gfc_init_options, gfc_handle_option): Handle the
	new option.

	* runtime/backtrace.c: New file.
	* runtime/environ.c (variable_table): New GFORTRAN_ERROR_BACKTRACE
	environment variable.
	* runtime/compile_options.c (set_std): Add new argument.
	* runtime/main.c (store_exe_path, full_exe_path): New functions.
	* runtime/error.c (sys_exit): Add call to show_backtrace.
	* libgfortran.h (options_t): New backtrace field.
	(store_exe_path, full_exe_path, show_backtrace): New prototypes.
	* configure.ac: Add checks for execinfo.h, execvp, pipe, dup2,
	close, fdopen, strcasestr, getrlimit, backtrace, backtrace_symbols
	and getppid.
	* Makefile.am: Add runtime/backtrace.c.
	* fmain.c (main): Add call to store_exe_path.
	* Makefile.in: Renegerate.
	* config.h.in: Renegerate.
	* configure: Regenerate.

From-SVN: r122954