Dynamic sized primitive array

[MaartenS11]

It would be nice for the primitive array to not be a global variable defined for each platform in a separate file. Instead, this primitive array can be a vector that a platform can register primitives in. This way some primitives can also be shared between primitives and the concolic execution engine can replace certain primitives with other primitives. Additionally, it reduces the increasing complexity of ifdefs that determine the number of primitives at compile time.

Needed for #324 and custom concolic primitives.