SDLU_FileDialog() bugs Windows

[Aggelos Kolaitis]

The Win32 implementation has the following bugs:

• The last character of the filename is for some reason truncated
• When called with 'mode = SDLU_FILEDIALOG_OPENDIR', only the chosen folder name is returned, not the full path to it.

[Aggelos Kolaitis]

Fixed #1: SDLU_FileDialog() truncated last character from filename (Windows)

→ <<cset 826fc172bff7>>