Lighttpd

This patch adds an option that will only execute a CGI script if its +x bit is set.
If the bit is not set the script will be treated as a normal file.

Together with cgi.execute-all, this can be used to execute all files that have +x
set and to not execute all files that don't have +x set. Some other httpds do this
(example: thttpd, gatling and probably quite a lot more). It removes the need to
flag all CGIs with an extension. (Extension based handling of stuff is not UNIX at
all and belongs to Windows software.)

The default setting is "disable" and will do nothing.

Applies to a720459