Implement a new command to show GDB build-time configuration parameters.

Implement a new command to show GDB build-time configuration parameters.

	* top.c (print_gdb_configuration): New function, displays the
	details about GDB configure-time parameters.
	(print_gdb_version): Mention "show configuration".

	* cli/cli-cmds.c (show_configuration): New function.
	(_initialize_cli_cmds): Add the "show configuration" command.

	* main.c (captured_main) <print_configuration>: New static var.
	<long_options>: Use it.
	If --configuration was given, call print_gdb_configuration.

	* doc/gdb.texinfo (Mode Options): Document '-configuration'.
	(Help): Document "show configuration".
	(Bug Reporting): Add requirements to include the configuration
	details in bug reports.