Correctly export all mod_dav public functions.

* modules/dav/main/mod_dav.h: Wrap all public functions in
  DAV_DECLARE or DAV_DECLARE_NONSTD.
* modules/dav/main/liveprop.c, modules/dav/main/props.c,
  modules/dav/main/util_lock.c, modules/dav/main/mod_dav.c,
  modules/dav/main/std_liveprop.c, modules/dav/main/util.c:
  Update function definitions.

Submitted by: Branko Čibej <brane xbc.nu>
Reviewed by:  Justin Erenkrantz, Paul Querna, Sander Striker


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.0.x@160188 13f79535-47bb-0310-9956-ffa450edef68