The Bulgarian hyphenation patterns contain a line consisting of '0ь0'
which has no practical effect on hyphenation. Add an exception in
roundtrip testing to make sure we don't fail while comparing our tables
with the input data.

Test: make -j works and creates .hyb files for bg and cu
Change-Id: Ia46b8a45fe522f5194d8105d31b34b0e27528cc9