Add debug redirect option

Add debug redirect option

Currently, when logging is enabled, output will be sent to both a
logfile and standard terminal output.  The redirect option sends output
only to the logfile.  This includes all debug output.

Add the option to redirect debug output seperately to normal
output, using the cli command:

  set logging debugredirect on

By setting this and enabling logging, all output and debug will
be sent to the logfile.  The user will still see all output but
no debug output.

This causes a change in behaviour for anyone currently using
logging redirect, as now only output will be redirected.  Users
will have to issue the additional command above to also redirect
debug.

Expand ui-redirect.exp cover the changes.

gdb/ChangeLog:

	* cli/cli-interp.c (struct saved_output_files): Add saved entry.
	(cli_interp_base::set_logging): Check debug_redirect.
	* cli/cli-interp.h (set_logging): Add debug_redirect parameter.
	* cli/cli-logging.c (debug_redirect): Add static variable.
	(pop_output_files): Add default param.
	(handle_redirections): Print debug setting.
	(show_logging_command): Likewise.
	(_initialize_cli_logging): Add debugredirect command.
	* interps.c (current_interp_set_logging): Add debug_redirect
	parameter.
	* interps.h (set_logging): Add debug_redirect parameter.
	(current_interp_set_logging): Likewise.
	* mi/mi-common.h: Likewise.
	* mi/mi-interp.c (mi_interp::set_logging): Likewise.

gdb/testsuite/ChangeLog:

	* gdb.base/ui-redirect.exp: Add debug redirect tests.