* input/regression/tuplet-gap.ly: new file.

* input/regression/tuplet-gap.ly: new file.

* lily/tuplet-bracket.cc (make_bracket): take gap interval.
(print): compute gap length from number size, include italic
correction.

* scm/define-grobs.scm (all-grob-descriptions): remove gap from
tuplet-bracket

* scm/paper.scm (set-default-paper-size): new function, to be
called at toplevel.
(set-paper-size): new function, to be called inside \paper {}
(set-default-paper-size): new function, to be called at toplevel.

* lily/paper-def.cc (LY_DEFINE): ly:paper-def?: new function.