Increase memory limits for IcedTea

[Florian Weimer]

* Andrew Haley:

> OK, so it's your complaint that MAP_NORESERVE shouldn't reserve memory
> even if overcommit_memory = 2 ?  That isn't what the documentation
> says:

No, my complaint is that before you increase the default heap sizes, you
should make sure that you still can run a decent number of VMs in
parallel even if overcommit_memory = 2 is set.

> This suggests to me that in Mode 2 the system is doing what it's
> supposed to do.

Maybe.  In this case, Hotspot should use a different method to reserve
the address space.  My concern is that the PROT_NONE trick works, but is
(AFAIK) not documented, and might break in the future.