Separation of publishing data in p2os interfaces.

Important: Patch was made against player CVS source tagged release-2-1-0rc1.

This patch fixes double (maybe even tripple) publishing of same data in p2os driver. It depends on the hardware and player configuration file (provided interfaces).

P2OS published same odometry data twice in Pioneer p3dx-sh (with gyro) when run with config file distributed with Player (config/pioneer.cfg), which provided all the interfaces.

I looked at the code, and figured it was due to first publishing at gyro data acquisition, and than again at acquisition of standard SIP.

I modified p2os.cc, p2os.h, sip.cc and sip.h to handle these (and other) interfaces separately. Also, I added time stamping of SIP packets in packet.cc Receive() method. I also included bare minimum for GlobalTime in packet.h, to be consistent.

Note: changes weren't thoroughly tested, but judging from the code (which wasn't heavily modified) and a simple test, it seems to work as intended. :)