Test the convenience functions $_gdb_setting and $_gdb_setting_str.

Test the convenience functions $_gdb_setting and $_gdb_setting_str.

gdb/testsuite/ChangeLog
2019-10-31  Philippe Waroquiers  <philippe.waroquiers@skynet.be>

	* gdb.base/setshow.exp: Test $_gdb_setting and $_gdb_setting_str.
	* gdb.base/settings.exp: Test all settings types using
	$_gdb_maint_setting and $_gdb_maint_setting_str in proc_show_setting,
	that now verifies that the value of "maint show" is the same as
	returned by the settings functions.  Test the type of the
	maintenance settings.
	* gdb.base/default.exp: Update show_conv_list.