* lily/general-scheme.cc (LY_DEFINE): elucidate docstring.

* lily/general-scheme.cc (LY_DEFINE): elucidate docstring.

* scm/define-markup-commands.scm (tied-lyric): new function: split
string along ~ and reattach with U+203F (tie character) and
negative space.

* scm/output-lib.scm (lyric-text::calc-text): new function.

* lily/lyric-engraver.cc (process_music): don't set 'text.

* scm/output-lib.scm (string-finger::calc-text): new function
(lyric-text::print): new function.

* scm/define-grobs.scm (all-grob-descriptions): add StringFinger