* Fix a bunch more rosdoc2 issues in rclcpp.
There are a smattering of problems in here:
1. We weren't properly using PREDEFINE for all of our macros.
2. The Doxyfiles were referencing tag files that may not exist
(this will be handled by rosdoc2 automatically).
3. The C++ parser in doxygen can't handle "friend classname",
but can handle "friend class classname"; it shouldn't matter
one way or the other to the compiler.
4. There were a couple of parameters that were not documented.
5. The doxygen C++ parser can't handle decltype in all situations.
6. There was a structure using a C-style declaration.
This patch fixes all of the above issues. We still aren't totally
clean on a rosdoc2 build, but we are a lot closer.
Signed-off-by: Chris Lalancette <clalancette@openrobotics.org>
