doc-src/Intro/gate.thy

added Classlib.* and Witness.*,
moved (and updated) Coind.*, Dagstuhl.*, Dlist.*, Dnat.*, Focus_ex.*
and Stream.* from HOLCF/explicit_domains to here
adapted several proofs; now they work again.
Hope that the following strange errors (when committing) do not matter:
rlog error: RCS/Classlib.ML,v: No such file or directory
rlog error: RCS/Classlib.thy,v: No such file or directory
rlog error: RCS/Coind.ML,v: No such file or directory
rlog error: RCS/Coind.thy,v: No such file or directory
rlog error: RCS/Dagstuhl.ML,v: No such file or directory
rlog error: RCS/Dagstuhl.thy,v: No such file or directory
rlog error: RCS/Dlist.ML,v: No such file or directory
rlog error: RCS/Dlist.thy,v: No such file or directory
rlog error: RCS/Dnat.ML,v: No such file or directory
rlog error: RCS/Dnat.thy,v: No such file or directory
rlog error: RCS/Focus_ex.ML,v: No such file or directory
rlog error: RCS/Focus_ex.thy,v: No such file or directory
rlog error: RCS/Stream.ML,v: No such file or directory
rlog error: RCS/Stream.thy,v: No such file or directory
rlog error: RCS/Witness.ML,v: No such file or directory
rlog error: RCS/Witness.thy,v: No such file or directory

Gate = FOL +
consts  nand,xor :: "[o,o] => o"
rules   nand_def "nand(P,Q) == ~(P & Q)"
        xor_def  "xor(P,Q)  == P & ~Q | ~P & Q"
end