ChangeSet was not sufficient to get the full ChangeLog between two
   released versions (when using "--changelog=last") as merging between 
   trees also merges the BK tags. Now we explicitely search for the last
   tagged ChangeSet that matches our major+minor version number, which 
   should match the last ChangeSet used for the previous release.


Build-tools/Bootstrap:
   - fixed a bug: simply searching for the last tagged ChangeSet was not
     sufficient to get the full ChangeLog between two released versions
     (when using "--changelog=last") as merging between trees also merges
     the BK tags. Now we explicitely search for the last tagged ChangeSet
     that matches our major+minor version number, which should match the
     last ChangeSet used for the previous release.