Support matrices and vectors on the shared heap

[andreaferretti]

These can be used by setting data to nil and setting fp directly. The data would have to be managed manually, much like most things on the shared heap. The approach is similar to what we do with the matrices and vectors on the stack.

A few functions need to be written to create these matrices and vectors on the shared heap, and the deallocate them, and then a few examples can be written. It would be nice to have an example where different threads work on independent slices of the data.