c.opt (Wpacked-bitfield-compat): Change init value to -1.

c.opt (Wpacked-bitfield-compat): Change init value to -1.

	* c.opt (Wpacked-bitfield-compat): Change init value to -1.
	* c-opts.c (c_common_post_options): If -W*packed-bitfield-compat
	was not supplied then set warn_packed_bitfield_compat to the
	default value of 1.
	* stor-layout.c (place_field): Check warn_packed_bitfield_compat
	against 1.

From-SVN: r143718