Merge branch 'harfbuzz-ng-external'

Conflicts:
	configure.in
	docs/tmpl/text-attributes.sgml
	modules/arabic/arabic-ot.c
	modules/indic/indic-ot.c
	pango/opentype/Makefile.am
	pango/opentype/hb-blob.c
	pango/opentype/hb-buffer-private.h
	pango/opentype/hb-common.h
	pango/opentype/hb-ot-layout-gsubgpos-private.hh
	pango/opentype/hb-private.h
	pango/pango-ot-info.c