PR 33721 load/store of misaligned address

PR 33721 load/store of misaligned address

This fixes PR33721 by a common technique of declaring a packed struct
to access unaligned integer fields.  (See eg. linux kernel
include/vdso/unaligned.h)  I've tidied the PR29856 fix for a similar
bug too (not that there was anything wrong with that fix).

	PR 33721
	PR 29856
	* sframe.c (flip_fre_start_address): Use a packed struct to
	access 2-byte and 4-byte unaligned fields.  Make addr a void*.
	(sframe_decode_fre_start_address): Similarly, and remove
	unnecessary casts.  Always set *fre_start_addr.