If two marks want to ligate and they belong to different components of the
same ligature glyph, and said ligature glyph is to be ignored according to
mark-filtering rules, then allow.
Example Burmese senquence:
U+1004,U+103A,U+1039,U+101B,U+103D,U+102D
Test font provided by Norbert Lindenberg.
Fixes https://github.com/behdad/harfbuzz/issues/545
Behdad Esfahbod