Platform specific header files get installed.  This allows plugins to be built with just an OpenMM installation, not a full source tree.
Merge branch 'headers' of https://github.com/peastman/openmm into headers
AmoebaMultipoleForce did not report particle groups, which could potentially lead to incorrect reordering
Merge pull request #47 from peastman/headers

Install platform specific header files, so plugins can be built without needing a full source tree
Merge pull request #48 from peastman/master

Fixed an atom ordering bug in AmoebaMultipoleForce
Fixed ACE and NME groups for modeller.
Merge pull request #51 from leeping/hydxmlfix

Fixed ACE and NME groups for modeller.
Merge https://github.com/SimTk/openmm
Merge branch 'master' of https://github.com/leeping/openmm
Changed some includes in test cases