* tree.h (unsave_expr_1): New function.
(lang_unsave): New variable.
(get_callee_fndecl): New function.
* tree.c (unsave_expr_now_r): New function.
(lang_unsave): Define.
(unsave_expr_1): Likewise.
(unsave_expr_now_r): Split out from unsave_expr_now.
(unsave_expr_now): Call lang_unsave if it is non-NULL. Otherwise,
call unsave_expr_now_r.
(get_callee_fndecl): Define.