Fix pointer subtraction implicit integer size cast.
Fix pointer subtraction implicit integer size cast.

Fixes a warning from clang.

tuscland/liblo,johne53/MB3Liblo,johne53/MB3Liblo,tuscland/liblo,radarsat1/liblo,radarsat1/liblo,johne53/MB3Liblo,johne53/MB3Liblo,radarsat1/liblo,tuscland/liblo