function.c: Include rtl-iter.h

function.c: Include rtl-iter.h

gcc/
	* function.c: Include rtl-iter.h
	(instantiate_virtual_regs_in_rtx): Turn from being a for_each_rtx
	callback to being a function that examines each subrtx itself.
	Return the changed flag.
	(instantiate_virtual_regs_in_insn, instantiate_decl_rtl)
	(instantiate_virtual_regs): Update calls accordingly.

From-SVN: r214640