* config/rx/rx.c (struct decl_chain): New local structure.
	(warned_decls): New local variable.  Contains a stack of decls for
	which warnings have been issued.
	(add_warned_decl): Adds a decl to the stack.
	(already_warned): Returns true if a given decl is on the stack.
	(rx_set_current_function): Issue a warning if multiple fast
	interrupt handlers are defined.
	* config/rx/rx.opt (mwarn-multiple-fast-interrupts): New option.
	* doc/invoke.texi: Document the option.

From-SVN: r192041