Cleanups for the exec server

[Justus Winter]

Hi :)

this is a series removing both functionality and unused
(out-#ifdef-ed) code in an attempt to reduce the size and complexity
of an essential server. Overall this cuts about 800 lines from
exec/exec.c.

It is meant to be applied over my recent patch series, but should be
applicable to the vanilla sources with a little fuzz. I'll rebase it
if anyone is in a hurry to get this in.

Discuss :)
Justus