Be consistant with Configure (which may be wrong but it's a start)

and assume Pthreads is only available with Solaris 2.5.0 and later


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@79170 13f79535-47bb-0310-9956-ffa450edef68