Add script to convert to new KDEInstallDirs variable names.

This is a separate script to adapt_cmakelists_file.pl, because it
produces CMakeLists.txt files that depend on e-c-m 1.6.0 or later, and
that may not be acceptable for all projects.

CCMAIL: kde-buildsystem@kde.org
CCMAIL: kde-frameworks-devel@kde.org