[CppAD] A Change to CppAD user interface.

[Brad Bell]

All the CppAD include file names have been moved to lower case and the
old file names have been deprecated. On Unix systems, it is necessary
to create a symbolic link in order to download new versions of CppAD and
still have your old source code (with the deprecated names) work. The
deprecated names, and the symbolic link, are documented in the web page
        http://www.coin-or.org/CppAD/Doc/include_deprecated.xml

This has also required changing CppAD to cppad in the subversion 
install; see
        http://www.coin-or.org/CppAD/Doc/installsubversion.xml

P.S.
For some reason, the version number of CppAD did not advance during the
build early this morning (but the current version does include the changes
that were committed yesterday). The current version of CppAD should be
20061204, but is 20061203 in the documentation. I have not yet figured out
why this is the case.
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