Save a few cycles and simlify code.

Use apr_pstrmemdup instead of apr_pstrndup when possible.
Avoid scanning the first 2 bytes when looking for the | delimiter. it is known to be "${".
Avoid comma separated statements, it is not that usual.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1830943 13f79535-47bb-0310-9956-ffa450edef68