Bug#2540: umsdos should depend on libg++27

[Michael Nonweiler <mrn20@hermes.cam.ac.uk>]

The umsdos utils are compiled with g++, and dynamically linked with
libg++.  They should therefore depend on libg++27.

Michael.

----
~# ldd /sbin/umssync
        libg++.so.27 => /usr/lib/libg++.so.27.1.0
        libstdc++.so.27 => /usr/lib/libstdc++.so.27.1.0
        libm.so.5 => /lib/libm.so.5.0.5
        libc.so.5 => /lib/libc.so.5.2.18
----