feature/gbuild_shell is finished

Hi all,

I have finished gbuild conversion of module shell, on branch
feature/gbuild_shell . It contains _a lot_ of platform-specific stuff,
mainly for Windows (and a big part of that is not even buildable with
mingw ATM), so it would be great if people threw it on their
tinderboxes/build machines to check it still builds (and works :-) If
you find a problem, feel free to push a fix or just yell at me and I
will try to remediate it.

Besides the conversion, I also removed one duplicate, kde-specific
header from vcl (so vcl now depends on shell) and updated gbuild module
gb_WinResTarget a bit (renamed some functions, added one or two new ones
and fixed dependency generation--I think it could never have worked as
it was).

I am going to let it sit still for about 2 weeks and then push it to
master, unless there are unforeseen problems.

D.