Optimized snowball code for tamil stemmer

I have replaced simple `or` conditions with `among()` command as suggested by Martin. I tried to use `among()` which consisted of some `test()` commands inside and they didnt work as expected so have left them as it is. I tested the modification against the data in https://github.com/rdamodharan/snowball-data/tree/master/tamil and the results were same.