Declare that sablecc-runtime is (also) licensed under the EPLv1.0

This matches the comments at the top of all of the sablecc-runtime
source files. I'm also leaving in the LGPLv2.1 as an alternative license
though - according to the FSF, the EPLv1.0 is incompatible with GPL
licenses, so the dual license is necessary to allow distributing our
SableCC fork. (All code in sablecc-runtime was written by us, so we're
free to relicense it like this.)