Collision between slurs and triolet indication

[Raphael Manfredi]

When putting slurs around triolets, the slur is overriding the "3".
The slur should be curved to avoid this overlapping.  Again, I think
this should be part of the "regression tests" because it's a basic
feature.

In the example here, I had to duplicate the measures so that enough
gets stuffed in the line for the problem to show up (using A4 paper).

------------------------------------------------------------------------
% The slurs should be shifted down to not overlap triolet indications
% or should be put up automagically.  Anyway, when slur is forced down,
% an automatic shift down to avoid hiding the "3" should be done.
\version "2.6.3"
\new Staff {
        \clef treble \time 2/4 \key f \major
        \override Staff.NoteCollision
                         #'merge-differently-dotted = ##t
        \relative c' {
                << f4\mp \\ \times 2/3 { f8( c a) } >>
                << g'4 \\ \times 2/3 { g8( e c) } >>
                |
                << f4 \\ \times 2/3 { f8( c a) } >>
                << g'4 \\ \times 2/3 { g8( e c) } >>
                |
                << f4 \\ \times 2/3 { f8( c a) } >>
                << g'4 \\ \times 2/3 { g8( e c) } >>
                |
                << f4 \\ \times 2/3 { f8( c a) } >>
                << g'4 \\ \times 2/3 { g8( e c) } >>
                |
        }
}
------------------------------------------------------------------------

Raphael