offsets and cast to apr_size_t before the bounds check so a
negative offset cannot bypass it, both for the direct read and
the indirect (INDIR) read.
Submitted by: arshiya tabasum <arshi bugqore.com>
GitHub: PR #757, closes#715
git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1938260 13f79535-47bb-0310-9956-ffa450edef68