. Add indirect dependency on roscpp-core in depend.mk

. Add a bunch of %-config.cmake in SYSTEM_SEARCH

The ros_comm stack contains the ROS middleware/communications packages. This
packages are collectively known as the ROS "Graph" layer. They provide
implementations and tools for topics, nodes, services, and parameters. This
includes the supported ROS client libraries: roscpp, rospy, and roslisp.