[Bundle request] nginx-mainline-extras to include nginx-dav-ext-module

[yw662]

Since nginx-dav-module is already included in nginx-mainline, there should be some bundles to ship nginx-dav-ext-module, for full webdav support.

Otherwise nginx-mainline should not be built with webdav support at all (which means, exclude nginx-dav-module from nginx-mainline) if nginx-dav-ext-module is not available.