Add the ability to pass flags to both apr_file_open and apr_mktemp.

The reason for this, is that it is very possible to want a temp
file that isn't deleted when the file is closed. It also makes sense
to have the flags in the apr_file_t if possible.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@92766 13f79535-47bb-0310-9956-ffa450edef68