message: Something subtle changed, force math defines
  Primarily needed to ensure that the cmath header defines M_PI, which
  stopped working on clean builds after the latest set of depdendency
  updates on a clean build (but not an incremental build as I tested).
diff: @@ -34,7 +34,7 @@ set_property(GLOBAL PROPERTY AvogadroLibs_PLUGINS)
  set_property(GLOBAL PROPERTY AvogadroLibs_STATIC_PLUGINS)
  if(MSVC)
  - add_definitions("-D_CRT_SECURE_NO_WARNINGS" "-DNOMINMAX")
  + add_definitions("-D_CRT_SECURE_NO_WARNINGS" "-DNOMINMAX -D_USE_MATH_DEFINES")
  endif()
  include_directories(BEFORE ${CMAKE_CURRENT_SOURCE_DIR}
  