mod_file_cache broken on Windows

[Bill Stoddard]

Or perhaps serving a cached file is tickling a bug in the bucket code.  To recreate, 
load
a file into the cache (use CacheFile) and pound on the server requesting the cached 
file
with apachebench.  Seg fault in apr_brigade_cleanup but the stack is completely 
trashed so
I can't see the calling chain.

Bill