[cairo] show_glyphs function of FT backend

[Peter Weilbacher (Mozilla)]

I recently noticed[1] that the show_glyphs function was removed
from the FT backend some time ago. I guess if there were postings
to this list about it, I missed them and I am not experienced
enough with git to find out why it was removed. Can somebody
give me a hint?

   Peter.

[1]: It seems that nobody on OS/2 was actually using anything
more than the toy text API until now, and I just noticed that
it's gone because I wanted to finally use glyphs for Mozilla on
OS/2 and no glyphs showed up any more...