GitLab

Converted the routine for identifying molecules from a recursion to a loop.  This avoids stack overflows with very long linear molecules.

Platform specific header files get installed.  This allows plugins to be built with just an OpenMM installation, not a full source tree.

Using a const Vec3& instead of three doubles for the AnisotropicBarostat API.  Still figuring out SWIG issues.

Converted the array containing atom block indices for the neighbor list from ushort2 to int.  This removes the hard limit of 2 million atoms.

Integrators control when atom reordering gets done, instead of having it happen automatically when forces are evaluated.  This simplifies some code, and also improves unintuitive behavior with CustomIntegrator.