* include/Partition.h,
src/Partition.cc: added 'Glib::ustring mountpoint'
* include/GParted_Core.h,
src/GParted_Core.cc: implemented set_mountpoints() to set mountpoint
in partitions.
* include/Dialog_Partition_Info.h,
src/Dialog_Partition_Info.cc: use Partition::mountpoint instead of
finding it ourselves.