Add tests parsing/generating msg/srv/action comments with non-ASCII characters

[gavanderhoorn]

As discussed in https://github.com/ros2/rcl_interfaces/pull/147:

[..] tests for non-ascii characters in comments in message files [..]

should be added to the appropriate packages.

https://github.com/ros2/rcl_interfaces/pull/147 removed a couple of unicode apostrophes, which could be seen as having been:

[tests for] support [of] Unicode inside of comments in .msg files [..]

As those characters were removed in https://github.com/ros2/rcl_interfaces/pull/147, proper tests should be added here in ros2/rosidl to replace them.