Fix mod_so handling. Basically, if --enable-so or

--enable-some-module=shared is specified on the ./configure line, then
mod_so is included in the build, -ldl is added to LIBS, and --enable-dso is
added to APR's configure line.  Otherwise, mod_so is turned off, -ldl is
not added, and APR is specifically told to build without DSO support.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@85418 13f79535-47bb-0310-9956-ffa450edef68