[XeTeX] texlive13/harfbuzz problem with nastaleeq font

[Kamal Abdali]

The files using a nastaleeq font (Jameel Noori Nstaleeq) which were
processed quite well under texlive12/xelatex/polyglossia are being typeset
with lots of very overfull lines under texlive13. I tried various settings
of the fontspec WordSpace option, \pretolerance, etc, but they didn't
improve the output. The same files are still typeset in TL13 very nicely
when I switch to a naskh font (XB Zar).

Attached are a source file and its pdf outputs with nastaleeq font in TL 12
& 13 and with naskh font in TL13. I'm sorry the files are long but shorter
files didn't illustrate the problem well. I'll provide links to the fonts
if a solution doesn't suggest itself to some expert by just looking at the
files here.
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