GitLab

                                     overrides of bonded gathers for testing
BrookGbsa:                           OBC parameters fixed; added energy calculation
BrookCommon:                         added utility methods for allocating arrays

1) Added DLL export macros to many classes; enough to get tests to compile
2) Cosmetic changes to reduce warnings in Visual Studio:
   a) change many "for (int i ="... to "for (size_t i ="... to avoid unsigned mismatch warnings
   b) included many explicit static_cast<OpenMMReal>() casts to document places where double->float conversion warnings occur

OpenMM/CMakeLists.txt, to probably help build when invoked from
directory above.