Smarter memory allocation mechanism in SPI

[tylergu]

Currently SPI finds free intervals between objects and tries to find a free interval for each CodeObject. A better memory allocation mechanism should be developed.

Ideally we should have a single pool of memory for all CodeObject, and memory allocation requests would look for a chunk of memory within a specific range. When this pool runs out of memory, we would mmap more memory from the free intervals based on the /proc/$pid/maps file.

Right now we are trying some simpler workarounds.

[tylergu]

A work around is implemented by PR #13

[Ethane98]

When objects are loaded without large enough free intervals between them, SPI must malloc a new buffer and install a long jump for each mapped object. A smarter memory allocator could map multiple objects into one buffer as a future optimization.