[mod_webdav] major rewrite (fixes #1818)
[mod_webdav] major rewrite (fixes #1818)

(occurred 3 years ago on experimental branch, and now ported forward)

robustness and performance improvements, including atomic updates on
individual files (e.g. for PUT, COPY, MOVE)

exclusive locks are fully supported
shared locks are partly supported

x-ref:
  "add RFC-compliant LOCK support to mod_webdav"
  https://redmine.lighttpd.net/issues/1818

lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4