vcl quartz: cache per-run glyphs information

GetNextGlyphs could only deal with 1 glyph at the time
and was recalculing a lot of thing while iterating on the glyphs

This is not just a performance issue.. the notiong of keeping
per run glyphs information will be useful to re-establish the
proper support of glyphs display positionning by SetDXArray()
which today is completely ignored, in favor or letting
CoreText spread the extra free space itself.

Change-Id: Ib267c3e490619b650d4149f4b15b5758802942ba
Reviewed-on: https://gerrit.libreoffice.org/8879
Tested-by: Norbert Thiebaud <nthiebaud@gmail.com>
Reviewed-by: Norbert Thiebaud <nthiebaud@gmail.com>