Bug#237649: kde does not depend on xserver

[jkn@softavenue.fi]

Package: kde
Version: 4:3.1.2
Severity: normal

We made a test installation with daily bootfloppies.  Tasksel did not
work (perhaps change unstable -> testing confused it).  I said to
installers: "Install kde and you'll get everything you need."  It
didn't work, because xserver did not get selected.  

I don't see any reason why kde should not depend on xserver.
xserver-xfree86 'Provides: xserver'.  All xservers don't provide
'xserver', but that is easy to fix.

Installing should be made as easy as possible for inexperienced users.
(All new users are more or less inexperienced.)