Added SUM-CLAUSE parsers to global list of clause parsers.
Added SUM-CLAUSE parsers to global list of clause parsers.

clasp-developers/SICL,vtomole/SICL,vtomole/SICL,clasp-developers/SICL,clasp-developers/SICL,vtomole/SICL,vtomole/SICL,clasp-developers/SICL