libtiff:
 * bump version to 3.9.7
 * makefile fixes, cleanups, typo fixes
 * fix external not available in menuconfig
 * provide C++ version of the library
 * refs #1726


git-svn-id: file:///var/svn/freetz/trunk@10082 149334a1-2f27-0410-a3b9-fc62619ac1e6