- Remove pymol::destroy from freeP
- Remove vla(size, value) constructor (was only used for testing). It
was using VLAlloc. Now VLACalloc is the only allocator used.
- Remove unused std::vector adaptors
- remove ambiguity of pymol::vla(0)
- add nullptr assignment (instead of nullptr construction)
- empty initializer list behaves like default constructor
- new factory function to take ownership of legacy VLA (only used in tests)