Fix a Solaris compilation problem with mod_cgid:

Use <sys/un.h> to get sockaddr_un.  Previously we declared it ourselves
for unknown reasons.  I am now able to compile on Linux (RH6.1), Solaris
8, and FreeBSD 3.4.  Also, I don't see a mention in UNP V1 (2e) of the
need to play tricks to get sockaddr_un.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@85498 13f79535-47bb-0310-9956-ffa450edef68