Merge branch 'master' of ssh://jomand@git.sv.gnu.org/srv/git/lilypond

* 'master' of ssh://jomand@git.sv.gnu.org/srv/git/lilypond:
  Typo.
  Markup command documentation: categories and properties
  GDP: Process comments on LM 3 (A)
  Document argument limitations of `define-markup-command'.
  Updated the NR title to "Notation Reference"
  Remove `foo.txt'.