Don't delete iconv locale data from the appliance.

- /usr/lib{,64}/gconv/*:

This is the iconv data, required for APIs like iconv_open to work.  In
particular, the mtools 'mcopy' program fails completely if it cannot
use iconv.  'mcopy' is used by SYSLINUX to copy files to the disk.

The error you would have seen is:

  Error converting to codepage 850 Invalid argument
  Cannot initialize 'S:'
  Bad target s:/ldlinux.sys

- /usr/bin/localedef and /usr/sbin/build-locale-archive:

These are not really needed, but both are simply small binaries so we
might as well not delete them.
New APIs: Add support for syslinux and extlinux (bootloaders).

This also adds tests of SYSLINUX and EXTLINUX which create bootable
guests.