Add support alloc-free

[CapZTr]

This PR adds support to detect heap memory safety issues in:

1. adding new event MemFree with new tag FREE
2. modifying event MemAlloc (renamed from Alloc), which has new tag ALLOC when it is a heap allocation
3. enhancing alias analysis to handle the two events above
4. adding new event Termination with tag TERMINATION which gets executed if and only if the program terminated normally
5. adding new base relation AllocPtr and AllocMem and derived ones into models c11 and rc11, NOTE: vmm is still WIP