Skip a few bytes before calling 'strchr' if we know that they can't match.

s/apr_pstrndup/apr_pstrmemdup/ when applicable.
Fix a comment typo.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1683044 13f79535-47bb-0310-9956-ffa450edef68