libsframe misaligned uint32_t

libsframe misaligned uint32_t

I saw asan complaints about misaligned loads and stores when taking a
quick look at pr33810 before Jens' patch was applied.  They have
disappeared now, but it looks to me like a FRE can start on any
address boundary and there is no padding or suchlike to align the
FRE fields.

	* sframe.c (flip_fre_stack_offsets): Let the compiler know
	that integers may be misaligned.