[core] return 501 Not Implemented in static file mode for all methods except GET/POST/HEAD/OPTIONS

git-svn-id: svn://svn.lighttpd.net/lighttpd/branches/lighttpd-1.4.x@2882 152afb58-edef-0310-8abb-c4023f1b3aa9
[core] recognize more http methods to forward to backends (fixes #2346)

git-svn-id: svn://svn.lighttpd.net/lighttpd/branches/lighttpd-1.4.x@2883 152afb58-edef-0310-8abb-c4023f1b3aa9