Fix crash on Windows when a project could not be opened. Remove prefix from win32_get_file_filters() and win32_get_filters(). Fix some encoding problems with filenames retrieved from the native Windows file dialogs.

git-svn-id: https://geany.svn.sourceforge.net/svnroot/geany/trunk@2238 ea778897-0a13-0410-b9d1-a72fbfd435f5