Before, that was printed using --debug (and in both hb-shape and hb-view).
Changed it, now hb-shape has a new command-line argument called --show-messages.
When invoked, it also respects other output formatting options.  The messages
are better formatted and printed to te same place that hb-shape output is
directed to.  Previously they were written to stderr.

Fixes https://github.com/behdad/harfbuzz/issues/506

Also makes hb-view to use 8 bits of subpixel precision and shape at
requested size, instead of always shaping at upem and scaling results.

https://bugs.freedesktop.org/show_bug.cgi?id=65544

Use with Arabic, for example, to see the effect on joining.

Computes all the glyphs that may be generated given a font and
set of Unicode characters.

The order of the Unicode characters is irrelevant.

Sample output:

behdad:util 0$ ./hb-ot-shape-closure Doulos\ SIL\ Regular.ttf f
f f_f

behdad:util 0$ ./hb-ot-shape-closure Doulos\ SIL\ Regular.ttf i
i

behdad:util 0$ ./hb-ot-shape-closure Doulos\ SIL\ Regular.ttf fi
f f_i f_f_i f_f i

behdad:util 0$ ./hb-ot-shape-closure DroidNaskh-Regular.ttf ب
uni0628 uni0628.init uni0628.medi uni0628.fina

behdad:util 0$ ./hb-ot-shape-closure DroidNaskh-Regular.ttf ا
uni0627 uni0627.fina

behdad:util 0$ ./hb-ot-shape-closure DroidNaskh-Regular.ttf با
uni0627 uni0627.fina uni0628 uni0628.init uni0628.medi uni0628.fina

behdad:util 0$ ./hb-ot-shape-closure DroidNaskh-Regular.ttf با --no-glyph-names
5 6 133 134 135 136