windows.c: Change the current process path to the module path

When an executable is started on Windows, it has a "Working
directory". This directory for a program shortcut stored on the
Desktop can be different than the actual executable directory.
This also applies if a shell extension is registered to that
executable (in the case of Subsurface that could be a .DLD file).

When another process simply "executes" a file with a certain extension
(e.g. when you double click on a .DLD file), a method ShellExecute
is called, which without explicit parameters sets the "Working
directory" to the .DLD file directory. This can be a bit of a trouble
if the executed module depends on relative paths (e.g. ./xslt, ./share).

To solve that we obtain our module full path and filename using
GetModuleFileName(), strip the filename from it (e.g. subsurface.exe)
and then pass the resulted string to SetCurrentDirectory(), which
updates the "Working directory".

Signed-off-by: Lubomir I. Ivanov <neolit123@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Remove ancient (and unwanted) Debian packaging directory

The Debian maintainers prefer this to be separate from the upstream
sources

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>