src/libpcp_web/src/exports: remove pmDiscoverRegister and pmDiscoverUnregister
src/libpcp_web/src/exports: remove pmDiscoverRegister and pmDiscoverUnregister

Breaks the Solaris/OpenIndiana build, expect this to come back when
the rest of this work is really ready to go.

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