Yosemite v2.3.1

Minor fixes of release v2.3.0 (df94cf68b9d9d813e4d781c7edb9ac638724dadf) to build on OS X 10.10.1, Yosemite via the CMake route, not qmake.

Given that a lot of the files move in the next refactoring, these changes will not carry over automatically. I'd like to provide the GitHub community a visibly working build for Yosemite of IQmol.

Cheers,
Joe