Bring part some parts of r1142938 which were removed

by the big ldap revert r1150179.

Original commit log:

Use APR_ADDTO instead of APR_SETVAR or direct
variable assignment.

...


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1150231 13f79535-47bb-0310-9956-ffa450edef68