Strengthen fields in struct sequence_stack and struct emit_status

Strengthen fields in struct sequence_stack and struct emit_status

gcc/
2014-08-26  David Malcolm  <dmalcolm@redhat.com>

	* function.h (struct sequence_stack): Strengthen fields "first"
	and "last" from rtx to rtx_insn *.
	(struct emit_status): Likewise for fields "x_first_insn" and
	"x_last_insn".

	* emit-rtl.h (get_insns): Remove now-redundant checked cast.
	(set_first_insn): Add checked cast.
	(get_last_insn): Remove now-redundant checked cast.
	(set_last_insn): Add checked cast.

	* config/m32c/m32c.c (m32c_leaf_function_p): Strengthen locals
	"saved_first" and "saved_last" from rtx to rtx_insn *.

From-SVN: r214537