Use DEPRECATION instead of WARNING for package deprecation messages
Use DEPRECATION instead of WARNING for package deprecation messages

This makes it possible to treat the warnings differently in downstream packages.
Refer to the CMake documentation for more info: https://cmake.org/cmake/help/v3.0/command/message.html

Signed-off-by: Jose Luis Rivero <4718c3fb94836e2654e01497a98fab353726b9c0@osrfoundation.org>

ament/ament_cmake,ament/ament_cmake,ament/ament_cmake