Revision 15629 (8d71734a0cb0) removed the serverConn interface
that was introduce in revision 7718 (ee5e80c62862).  The
serverConn interface was there for use by gccgo on Solaris,
and it is still needed there.  Solaris does not support
connecting to the syslog daemon over TCP, and gccgo simply
calls the C library function.  This CL restores the
interface.

R=golang-dev, bradfitz, rsc
CC=golang-dev
https://golang.org/cl/11737043