The function SB-BSD-SOCKETS:GET-PROTOCOL-BY-NAME did not signal
an error when it was unable to find a protocol. This is fixed now
and an error of type UNKNOWN-PROTOCOL, with an accessor named
UNKNOWN-PROTOCOL-NAME, is being signaled. These two names are also
exported from the package SB-BSD-SOCKETS.
A test case is added.
Several other test cases are fixed with regard to :NO-ERROR clauses
inside HANDLER-CASEs.