Fix the C example programs still using the legacy RA interface to
eliminate a potential crash due to a missing callback function.  Also
make these programs compile without warnings on -Wall.

* tools/examples/svnput.c, tools/examples/headrev.c: Add missing includes.
  (open_tmp_file): New function.
  (main): Add open_tmp_file to the callback table passed to the RA
    layer.  Remove unused variables.

* tools/examples/getlocks_test.c: Same as all above, plus...
  (my_commit_callback): Remove function, not used.

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Fix the C example programs still using the legacy RA interface to
eliminate a potential crash due to a missing callback function.  Also
make these programs compile without warnings on -Wall.

* tools/examples/svnput.c, tools/examples/headrev.c,
  tools/examples/getlocks_test.c: Add missing svn includes.
  (open_tmp_file): New function.
  (main): Add open_tmp_file to the callback table passed to the RA
    layer.  Remove unused variables.

Also, one further change to getlocks_test.c:

* tools/examples/getlocks_test.c
  (my_commit_callback): Remove function, not used.