Include required 'debug.h' file.

  This updates #111.
  Added simple CFile::basename() method.

  This closes #111.
  Updated include-files.

  We prefer to forward-declare classes rather than including
 header-files willy-nilly.
  Updated changelog since 111 will be closed by the next release.
  Removed duplicate #includes.

  These includes were found via the new style-check:

        style/style-multiple-includes.t
  Added new style-test.

  This script tests that we don't include a header file more than
 once per source-file.

  For example this is bogus:

    foo.cc:
        #include "header.h"
        #include "foo.h"
        #include "header.h"

  (Because "header.h" is included twice.)
  Ran this script through perltidy.

  Just for neatness, no functional changes just formatting.
  Allow "--rcfile path" to be specified multiple times.

  As suggested by Paul Dobson via private mail.