Add instructions on building lighttpd for Debian stable.

Some Owncloud features (Namely contact editing) don't work with Lighttpd on Debian stable because it doesn't support the PATCH verb. Add instructions on how to patch that functionality in and build the resulting package.
installation_others.rst: Remove extra newlines
Merge pull request #227 from ssweeny/patch-1

Add instructions on backporting HTTP PATCH support to Debian stable's Lighttpd