This is actually for beta4pl1, but there's no option in the selector for it yet...

ext/dav/php_dav.h, line 46, reads:
<pre>
int phpdav_mkcol_test_handler(request_rec *);
</pre>
It should read:
<pre>
int phpdav_mkcol_test_handler(request_rec *r);
</pre>
I also had to add
<pre>
#include "httpd.h"
</pre>
to the start of that file in order to define the request_rec struct. In addition, ext/dav/dav.c, line 159, reads:
<pre>
PHP_MINFO_FUNCTION(phpdav);
</pre>
It should read:
<pre>
PHP_MINFO_FUNCTION(phpdav)
</pre>
Making these changes allow the module to compile, but there are still some warnings about making ints from pointers without casting.