feature request: show if installed for "port search"

[Roger Pack]

Hello.
Currently we have:

$ port search dvdnav
libdvdnav @4.1.3 (devel, multimedia)
    DVD navigation library

Feature request/suggestion

$ port search dvdnav
libdvdnav @4.1.3 (devel, multimedia) (installed)
    DVD navigation library

Cheers!
-roger-