* Adjust etag generation to produce identical results on 32-bit and 64-bit

  platforms and avoid a regression with conditional PUT's on lock and etag.

  Add a warning to the documentation of FileETAG that changes of the ETAG
  format can cause conditionals to fail on mod_dav_fs provided backends.

PR: 44152
Submitted by: Michael Clark <michael metaparadigm.com>
Reviewed by: rpluem


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@607437 13f79535-47bb-0310-9956-ffa450edef68