Fix aio.c for linux
Fix aio.c for linux

struct timespec does not have a tv_nanoseconds field http://en.cppreference.com/w/c/chrono/timespec
the addIdleUsecs must be declared before used: I've factored the declaration outside first use because modern gcc require it.

timfel/squeakvm,peteruhnak/pharo-vm,timfel/squeakvm,OpenSmalltalk/vm,peteruhnak/pharo-vm,OpenSmalltalk/vm,timfel/squeakvm,OpenSmalltalk/vm,peteruhnak/pharo-vm,timfel/squeakvm,OpenSmalltalk/vm,timfel/squeakvm,timfel/squeakvm,peteruhnak/pharo-vm,peteruhnak/pharo-vm,peteruhnak/pharo-vm,timfel/squeakvm,OpenSmalltalk/vm,timfel/squeakvm,OpenSmalltalk/vm,OpenSmalltalk/vm,peteruhnak/pharo-vm,OpenSmalltalk/vm,peteruhnak/pharo-vm