I've been advised on Debian Devel IRC mainly by juliank to stick
to libtesseract3 and not do libtesseract3a. See bug 815056.
Personally, I am in over my head but the IRC folks sound confident
that this is the right course of action.
P.S. Tersseract 3.04.01-4 has a breaks/replace against the ill fated
and short lived libtesseract4.