src/libpcp/src/fix_derive_parser_y: bison version 2.7 needs the old way
src/libpcp/src/fix_derive_parser_y: bison version 2.7 needs the old way

Despite the Bison documentation claiming the change was made in
version 2.6, I have a QA machine with Bison 2.7 that is failing,
so revert to the old way for 2.6 and 2.7.

adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp