Remove make_cleanup_restore_current_language

Remove make_cleanup_restore_current_language

This patch replaces make_cleanup_restore_current_language with an RAII
class that saves the current language, and restores it when the object
is destroyed.

ChangeLog
2017-08-03  Tom Tromey  <tom@tromey.com>

	* utils.h (make_cleanup_restore_current_language): Remove.
	* utils.c (do_restore_current_language)
	(make_cleanup_restore_current_language): Remove.
	* parse.c (parse_exp_in_context_1)
	(parse_expression_with_language): Use
	scoped_restore_current_language.
	* mi/mi-main.c (mi_cmd_execute): Use
	scoped_restore_current_language.
	* language.h (scoped_restore_current_language): New class.