Creates a Flag grob. (issue 4922042)

[mtsolo]

Reviewers: ,

Message:
This should do the trick.

The regtests don't really help as they show tons of fake changes.  I'll
try Han Wen's suggestion for hacking output-distance.py in the next week
if I am still having trouble.

The only thing that currently seems broken is
stem-tremolo-note-column.ly.  This is because, as I state in my patch on
stem-tremolos, the stem tremolo pure height function is broken.  So, I
don't consider this a regression...

The order that this stuff would be pushed is:

This patch
The stem changes
My rewrite for stem-tremolo pure height stuff, which would be rewritten
yet again to be cleaner and more accurate in function of the pure height
changes to stem.cc

Cheers,
MS

Description:
Creates a Flag grob.

Please review this at http://codereview.appspot.com/4922042/

Affected files:
  M input/regression/color.ly
  M input/regression/flags-default.ly
  M input/regression/flags-in-scheme.ly
  M input/regression/flags-straight-stockhausen-boulez.ly
  M input/regression/flags-straight.ly
  M input/regression/graphviz.ly
  M input/regression/grid-lines.ly
  M input/regression/les-nereides.ly
  M input/regression/mozart-hrn3-defs.ily
  M input/regression/quote-overrides.ly
  M lily/beam-quanting.cc
  M lily/dot-column.cc
  A lily/flag.cc
  M lily/include/stem.hh
  M lily/stem-engraver.cc
  M lily/stem.cc
  M lily/tie-formatting-problem.cc
  M ly/engraver-init.ly
  M ly/grace-init.ly
  M ly/gregorian.ly
  M ly/property-init.ly
  M scm/define-grob-properties.scm
  M scm/define-grobs.scm
  M scm/flag-styles.scm