Backport two patches.

1. dup the apr_mmap_t out of the request pool for sending down the brigade. This
eliminates a segfault when serving MMapFile cached files

2. Fix a problem wherby multiple MMapFile directives would cause a segfault on
startup

PR: 16313


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/APACHE_2_0_BRANCH@98543 13f79535-47bb-0310-9956-ffa450edef68