Changes of version 15.3.0

• Add characters (#1337):
  • SUMMATION TOP (U+23B2);
  • SUMMATION BOTTOM (U+23B3);
  • BLACK RIGHT-POINTING DOUBLE TRIANGLE (U+23E9);
  • BLACK LEFT-POINTING DOUBLE TRIANGLE (U+23EA);
  • BLACK UP-POINTING DOUBLE TRIANGLE (U+23EB);
  • BLACK DOWN-POINTING DOUBLE TRIANGLE (U+23EC);
  • BLACK RIGHT-POINTING DOUBLE TRIANGLE WITH VERTICAL BAR (U+23ED);
  • BLACK LEFT-POINTING DOUBLE TRIANGLE WITH VERTICAL BAR (U+23EE);
  • BLACK RIGHT-POINTING TRIANGLE WITH DOUBLE VERTICAL BAR (U+23EF);
• Enlarged U+02BE and U+02BF to match the dimensions of other quotes (#1346).