* x86 recipes: emit StackOverflow trap for all sp-relative loads and stores
* x86 recipes: emit StackOverflow trap for push and pop
* x86 binary filetests: add stk_ovf trap annotations
Choosing smaller instruction encodings on eg. x86 is an optimization,
rather than a useful discrete setting.
Use "is_compressed" only for ISAs that have an explicit compression feature
that users of the output may to be aware of, such as RISC-V's RVC or
ARM's Thumb-2.