[x86_64] reserve a non-tiny amount of heap space for now
[x86_64] reserve a non-tiny amount of heap space for now

TODO: this is Bad, heap should grow dynamically from frame alloc?

rachlmac/sos-kernel,rachlmac/sos-kernel,rachlmac/sos-kernel,hawkw/sos-kernel,hawkw/sos-kernel,hawkw/sos-kernel