rtt_roscomm: fix output directory for generated typekit headers

8dbf5048d96abd4d8036c55c6b9eff78208b983c broke installation of typekit headers, as they have been generated without the `orocos/` component in the path and therefore have not been covered by the install rule in [GenerateRTTROSCommPackage.cmake.em#L230](https://github.com/jhu-lcsr-forks/rtt_ros_integration/blob/41be612568f23641fd950ba014800da0eb2a6661/rtt_roscomm/cmake/GenerateRTTROSCommPackage.cmake.em#L230).