similar(), and simple() as unused.
* libmisc/loginprompt.c: Tag the `sig' parameter of login_exit()
as unused.
* src/expiry.c: Tag the `sig' parameter of catch_signals() as
unused.
* src/su.c: Tag the `sig' parameter of catch_signals() as unused.
* src/su.c: Add int parameter to the prototype of oldsig().
* src/login.c: Tag the `sig' parameter of alarm_handler() as
unused.
* src/sulogin.c: Tag the `sig' parameter of catch_signals() as
unused.
* libmisc/getdate.y: Tag the `string' parameter of yyerror() as
unused.
* libmisc/getdate.y: The string provided to yyerror() is const.
* libmisc/getdate.y: Fix the prototypes of yylex() and yyerror().
