Doxgen commands: newline, details, copydoc, copybrief, copydetails

[anarthal]

I'm using the following commands, which are not yet implemented in mrdocs, and make migration harder:

• \n for newlines
• \details to start the detailed description section
• \copybrief, \copydoc, \copydetails to copy parts of the docs and avoid duplication (this last one is specially important to Asio-based libs, where many extremely similar overloads exist for the same function).

[sdkrystian]

\copybrief, \copydoc, and \copydetails are already implemented... however, disambiguating between overloads isn't currently implemented as it requires clang support.