Misc. Doxygen build system improvements
- Check Doxygen version when running one of the Doxygen targets, and
produce a note that states the expected version if there is a
mismatch.
- Check the result of the Doxygen process and fail the build if the
program returns an error code.
- Add a tag to all warnings that identify the type of documentation that
produces them. This should make it easier to understand the Jenkins
warnings in the case not all documentation types produce a certain
warning.
Change-Id: I030c0b2c69958fe41f0b964399cb1c2e1b250e77