Major changes:
- Add -E option that enables DVIPDFM emulation mode in DVIPDFMx.
- Don't try to convert included PDF files whose version number
is higher than output file version. (If run as dvipdfm,
conversion still occurs.)
- Added dvipdfm compatibility mode. This mode is triggered
if dvipdfmx is called as "dvipdfm", and likewise extractbb
as "ebb". (The latter mode was already present.)
- Made predefined paper sizes match values given by libpaper.
