Add stack allocator - will not be used yet, but will be added as part of pooling implementation
Initial karatsuba implementation - can be simplified - has memory leaks
Fix build
Expose absolute value method
Add test for large integer multiplication
Organize methods
Enable naive/karatsuba selection
Begin implementation of auto-free, add custom alloc/dealloc/stackalloc
Switch to canonacalizing, start organizing code, fix a few memory issues
In future commit will have a re-work of memory model to simplify/optimize
Fix some memory leaks in BigInt.c
Fix typo