Handle error conditions in dbd_construct() properly. Simplify

ap_dbd_open() and use correct arguments to apr_dbd_error() when
non-threaded.  Register correct cleanup data in non-threaded
ap_dbd_acquire() and ap_dbd_cacquire().  Clean up configuration data
and merge function.  Use ap_log_error() wherever possible.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@491884 13f79535-47bb-0310-9956-ffa450edef68