xxA() interfaces and wchar_t in some places. Add a static cleanup retry
method to TempFile, called after clearing the MimeHandler cache (killing
the subprocesses which might hold an open file).
Exchange file names and command line parameters with the system using
wchar_t interfaces: allows preserving values which can be reversibly
transcoded in the current multibyte charset (which can't be UTF-8). Store
all file paths internally in UTF-8
