* lily/my-lily-lexer.cc (My_lily_lexer): don't crash

* lily/my-lily-lexer.cc (My_lily_lexer): don't crash
on unquoted strings before \notenames.

* lily/parser.yy (lyric_element): allow markup as lyric text. This
increases the number of s/r reductions to 4.

* scm/new-markup.scm (fraction-markup): \fraction command.

* lily/lexer.ll: allow any string without \ { }  # and " in \markup
mode

* lily/lookup.cc (round_filled_box): rename function.
(LY_DEFINE): round-filled-box: change signature.

* Documentation/user/refman.itely: revise section explaining grace
notes.

* lily/my-lily-lexer.cc: add \accacciatura and \appoggiatura

* ly/grace-init.ly (stopGraceMusic): add slurs on grace note by
default

* ly/engraver-init.ly (ScoreContext): new property graceSettings.