Don't let the default handler try to serve a raw directory. At

best you get gibberish.  Much worse things can happen depending
on the OS.

This can happen when autoindex isn't loaded.

On AIX, I had a directory file which was reported to be 1536 bytes
in size.  mmap() failed so we went to the fall-back logic.
The first read() got 624 bytes and the next read() got 0
(supposedly EOF).  This confused us greatly, we kept allocating
buffers and reading and exercised the paging space.

Reviewed by:  Bill Rowe


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@93071 13f79535-47bb-0310-9956-ffa450edef68