Fixes build on Windows.  Ouch!

Use pointers instead of references, in preparation for upcoming change.

We are not using it for anything lse it seems.

Nothing changed...

Eventually this will become part of a yet-to-be-written hb-ot cmdline
tool.

Was causing assertion failure in shape_plan().

The old code doesn't work with all fonts, as Khaled has reported.

Commit 4c4e8f0e broke contextual lookups
by making the recurse() function always return false.

Reported by Khaled.  Test case: لا in Amiri.

Untested.

All of collect_glyphs() complete and untested now.