factor out TAINT_NOT into S_adjust_stack_on_leave

All callers of S_adjust_stack_on_leave had TAINT_NOT before the call to
S_adjust_stack_on_leave. Factor it into the func to make the callers
smallers machine code wise. More things can be factored out into
adjust_stack_on_leave from its callers, but this particular change is very
easy.
Rename S_adjust_stack_on_leave

It now does more than that, so use a name that describes when it is
called, rather than what it does.