ros-robot-model is obsolete. The actual dependency is now on ros-urdf.

prf-gazebo-ros-control -> prf-gazebo-ros-pkgs
Fix depend.mk

To trigger a new build, now that the tarball is in place

Changes since 2.6.6:

* Makes the code possible for gazebo 2.2 and gazebo 7
  (this fixes build on 16.04)

This enables mk/sysdep/cmake.mk to automatically add the proper cmake variables
defining the dependency path.

While here, tidy the Makefile and uncomment required dependency on gazebo.

While here, tidy the Makefile dropping useless statements.

roscpp is in ros-comm not in roscpp-core

Needed to access specific part of talos-ros-control.