Fix formatting of Doxygen verbatim blocks

Fix the formatting of Doxygen \verbatim blocks. Blocks that exceed the maximum line length have to be protected with clang-format guards, so that the lines are not wrapped around the column's max width.

Additionally, convert some \verbatim blocks to \code, so that they are rendered as such.

Finally, enable Doxygen comment blocks in dsr-option-header.h that were not being rendered due to a missing * in the Doxygen starting comment. I'm not sure whether this was done on purpose by the authors or if it's a mistake. I can drop that commit, if needed.