General tidying and cleanups. THe functional changes:

Remove NOOP sed commands, and incorporate the pkg-deinstall message into pkg-plist.
Use install-strip as the INSTALL_TARGET rather than manually stripping libraries.

Technically it needs a PORTREVISION bump for the pkg-deinstall/pkg-plist thing,
but I'm going to need to bump PORTREVISION for some other changes soon and I'd
rather not force everyone to rebuild an extra time for a differently-phrased message.