doc: added missing closing doxygen brackets
doc: use @brief for single defines
doc: added missing titles
doc: fixed typos and other misspellings
doc: use @false instead of 0
doc: use doxygen li tags
doc: add to group instead of redefining
doc: fix typo in UDP header
doc: remove doxygen duplication
doc: removed broken doxygen struct tags
doc: removed superfluous (and broken) @file params
doc: fixed broken param descriptions
doc: fixed broken doxygen references
doc: fix remaining doxygen warnings
Merge pull request #2117 from OlegHahm/doxygen_eliminate_warnings

Doxygen eliminate warnings pt. 2