Heap allocation

[RealKC]

Currently reqvm programs cannot allocate programs on the heap. This should be rectified.

Models that I will likely add:

• C-like manual memory allocation and deallocation
• a GC (or more)

Design questions:

• do we want manual memory allocation to be mutually exclusive with the GC?
• should there be a way to force one model over the other anyway if the answer to the above is "no"?
• how do we treat pointers?
• should our instruction set be expanded to allow instructions to work directly on pointers?