test_ts2.py: Add testcase for merging units
ts2.py: Fix tsunit merge with not fuzzy units

If other unit is good then merge that and mark current unit not fuzzy.
Only test for ZWS in Python < 2.6
Add Urdu fullstop equivalent
Ignore capitalisation tests in Burmese

Fixes bug #2690
Add punctuation rules for Burmese fullstop