Add to MScore font a repeat dot glyph separate from augmentation dot.

SMuFL distinguishes between the augmentation dot and the repeat dot (used in repeat bar lines).

This patch:
- adds the MScore font a separate glyph for repeat dot. The glyph is encoded in the same code point used by SMuFL and is currently a simple reference to the augmentation dot.
- changes the BarLine class draw code to use this glyph instead of the augmentation dot.
Merge pull request #578 from mgavioli/SMuFL_mscore_add_repeat_dot

MScore font: add 'repeat dot' glyph