Make the new IO code use less memory.

[jlouis]

The new IO code can at time utilize quite large amounts of memory. This is due to the fact that the process is so lightweight it never gets garbage collected. Thus, it is never seen that the binary() data it has is dead and be collected.

It can be verified by executing the following from a shell:

 [garbage_collect(P) || P <- processes()].

This means we should probably build in some form of garbage collection into the system on a timer, so when a function has not been utilized for a short while, it will try to GC itself. Also, we should probably hack the fullsweep_after spawn_opt.

[ghost]

We could set the process to always perform a full sweep, in spawn_opt that would be:
{fullsweep_after, 0}

[jlouis]

That, and also have a small timeout of 1-5 seconds and then ask for a GC after this.

[ghost]

###As it is now on my fs-code branch

• File servers are always spawned with {fullsweep_after, 0}
• A file server will always garbage collect after 5 seconds of inactivity.
• An inactive file server which has performed a GC will not perform a GC again after 5 seconds of inactivity.

[jlouis]

Rawr, merged to master.