Update handling of fitzpatrick modifiers.
Update handling of fitzpatrick modifiers.

To handle forming emoji 'ligatures' in RTL contexts we generate
reversed ligature sequences for the GSUB table.  Formerly we only did
this when there was a ZWJ in the sequence, and full reversal worked
because we had no sequences with both fitzpatrick modifiers and ZWJ.
However, now we do.  Harfbuzz treats fitzpatrick modifiers as though
they were combining marks and so we need to as well so that GSUB data
is in the order Harfbuzz expects.  So we 'unreverse' these pairs.

mxalbert1996/emojione-android,dougfelt/noto-emoji,googlefonts/noto-emoji,moyogo/noto-emoji,dougfelt/noto-emoji,julroy67/noto-emoji,googlefonts/noto-emoji,googlei18n/noto-emoji,radiocane/noto-emoji,radiocane/noto-emoji,dougfelt/noto-emoji,googlei18n/noto-emoji,googlei18n/noto-emoji,moyogo/noto-emoji,googlefonts/noto-emoji,julroy67/noto-emoji