Fix building with DSO support. If any module is configured to be

compiled for shared support then APR_HAS_DSO is enabled and -ldl is
added to the LIBS variable.  -ldl may need to be modified based on
platform.  If no modules are designated as shared then APR_HAS_DSO is
disabled and nothing is added to LIBS.  In basic testing this compiled
without errors or warnings.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@85362 13f79535-47bb-0310-9956-ffa450edef68