[genmsg] msgs should have copy constructors (ros ticket #3469)

[tfoote]

This is pretty simple to implement, so I did.

NOTE: see also #2723

The attached msg_gen.py was modified from the Ubuntu 9.04 "latest" release.

The test file is not very formal, it just exercises the new API and prints to the console.

trac data:

• Owner: dthomas
• Reporter: baxelrod
• Reported at: Tue Apr 26 10:32:20 2011
• URL: https://code.ros.org/trac/ros/ticket/3469

[tfoote]

[baxelrod] FYI, I updated my attached files to work with the "unstable" release on 2011.05.25 to target the upcoming Electric Emys release.

[baxelrod-bdai]

@benaxelrod

[dirk-thomas]

This feature is already available for a long time - I think since the message generation has been rewritten for Fuerte. Therefore closing the issue.