Make sure to pass all variables defining the proper python version as found by
robotpkg, otherwise ros CMakeFiles may happily find python-3.2 and use it
instead of python<3, although this does not work in the end (at least ros-rx
does this and breaks on F17).

This is done in the common ros Makefile as this affects all packages.

Fix actionlib/script/genaction.py that was using harcoded "python" interpreter.

Install .msg files generated from .action under the correct path.

common_msgs contains messages that are widely used by other ROS packages. These
includes messages for actions (actionlib_msgs), diagnostics (diagnostic_msgs),
geometric primitives (geometry_msgs), robot navigation (nav_msgs), and common
sensors (sensor_msgs), such as laser range finders, cameras, point clouds.