Disk usage

%DISK_FREE return free disk space for specified folder in bytes (double)
% INPUT ARGUMENTS:
% * some_path - string, existing file or folder path. Should be global.
%
% USAGE:
% * disk_free('C:\temp'); % regular usage
% * disk_free('C:\temp\1.txt'); % path points to a file
% * disk_free('\\?\C:\temp'); % UNCW path
% * disk_free('\\\\C:\temp'); % UNCW path with with java-style prefix
% * disk_free('\\IMP\Ctemp'); % samba share folder
% *
%
% INVALID USAGE:
% * disk_free('\\IMP'); % samba share root. Results in error.
%
% * disk_free('C'); % Use 'C:' instead. Results in error.
%
% * disk_free('disk_free') % Matlab function. Results in [0 0 0]
% % or some other result, if corresponding
% % local file was found.
% % i.e. don't use local paths!
%
% NOTE:
% Would result in an error for an empty DVD-rom drive (disk not inserted).
% And similar cases.