Increase memory limit

[postcasio]

Btw, while we're here - I think this was brought up quite a long time ago, but currently SM is initialised with a 5MB heap. I did some stuff using CoffeeScript and dynamic compilation and found I hit the memory limit almost immediately. This was probably fine in the 90s but I think today we can safely increase it. Maybe to 128MB or something, I dunno - maybe it should be configurable.

[FlyingJester]

I think that, if 5 MB was only sometimes a serious issue, 128 MB or even 256MB should be so high that some other, fundamental issue will make Sphere unsuitable for any project that bumps into that barrier.