2.0.11 spuriously links master with libwrap

[Bitt Faulk]

The master/Makefile links master with libwrap, and it doesn't need it. 
On my OpenBSD system, this actually causes runtime linking errors, as
libwrap expects deny_severity and allow_severity to be supplied to it. 
The only place those symbols exist is in master/service.o, but that's
not linked in my master, only by the imap/* clients.

-Bitt