maintainer update to version 0.31.1
Please note that it bumps the shlib versionnumber.
PR: ports/47205
Submitted by: KANOU Hiroki <kanou@mil.allnet.ne.jp>
Autotrace port is updated to 0.31.0 by maintainer.
Shared library version is changed from 1 to 2 and
one port (graphics/frontline) is affected.
PR: ports/44846
Submitted by: KANOU Hiroki <kanou@mil.allnet.ne.jp>