Univention Corporate Server 4.1 erratum 311 (bugfix)

This update addresses the following issues:
* The Listener now checks the file system for enough free space and aborts,
  if too few is available. The default of 10 MiB can be changed through the
  new UCR variable 'listener/freespace'.
* The Listener now writes the state of each handler just after
  initialization.
* For each changed LDAP entry the distinguished name is now logged with debug
  level 'PROCESS'.
* Several quoting problems in the init and runit scripts have been fixed.
* Build-hardening and more warnings have been enabled for the compiler. Error
  handling and logging have been improved.