Included S-Lang updated to 1.4.5

[Pavel Roskin]

> So I decided to update S-Lang, and it was surprisingly easy.  To avoid 
> renaming slang.h to slang-mc.h I moved all includes to a separate 
> "include" directory.  This would prevent the configure script from picking 
> local slang/slang.h header when testing for the installed library.

As a side effect, everybody using patches should now use "patch -E" to 
make sure that the old headers are removed.

-- 
Regards,
Pavel Roskin