mtools: remove ignored configure options

The --enable-xdf, --enable-vold, and --enable-new-vold options were
actually not being passed to ./configure since they were specified on
the wrong variable (MTOOLS_CONF_OPT vs. HOST_MTOOLS_CONF_OPT) and mtools
is a host-only package. Fixing the variable name so that the options are
actually used ends up causing the build to fail due to linker errors.
Since vold identifiers and OS/2 XDF support are unlikely to be used any
more, remove them completely.

Signed-off-by: Frank Hunleth <fhunleth@troodon-software.com>
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>