* New function: gdbm_open_ext

This function provides a general-purpose interface for opening and
creating GDBM files.  It combines the possibilities of gdbm_open
and gdbm_fd_open and provides detailed control over database file
locking.

* New gdbmtool command: collisions

The command prints the collision chains for the current bucket, or
for the buckets identified by its arguments:

  collisions
     Display collisions for the current bucket.

  collisions N
     Display collisions for bucket N.

  collisions N0 N1
     Display collisions for the range of buckets [N0, N1].

* Pipelines in gdbmtool

The output of a gdbmtool command can be connected to the input of a
shell command using the traditional pipeline syntax.

* Fix a bug in block coalescing code

* Other bugfixes