Revert the sigaltstack changes in 352de13869ef1aefeae1c6f863eeb41111db7ffe given the fixes to the fundamental problem in VMMaker.oscog-eem.2570 et al. Keep the refactoring taht puts the sigaltstack code, if needed, in aio.c.
Revert the sigaltstack changes in 352de13869ef1aefeae1c6f863eeb41111db7ffe
given the fixes to the fundamental problem in VMMaker.oscog-eem.2570 et al.
Keep the refactoring taht puts the sigaltstack code, if needed, in aio.c.

timfel/squeakvm,timfel/squeakvm,OpenSmalltalk/vm,timfel/squeakvm,OpenSmalltalk/vm,timfel/squeakvm,timfel/squeakvm,timfel/squeakvm,OpenSmalltalk/vm,timfel/squeakvm,OpenSmalltalk/vm,OpenSmalltalk/vm,OpenSmalltalk/vm,timfel/squeakvm,OpenSmalltalk/vm,OpenSmalltalk/vm