This commit adds the ability to ccmake of cycling through cache options.
This uses the STRINGS property of the cache entry. The enter key will cycle
forward, and the right and left arrows will go up and down in the list.
Ensure CMAKE_DATA_DIR, CMAKE_DOC_DIR, and CMAKE_MAN_DIR are always
relative paths in CMake code, and set defaults accordingly. Use the
install() command instead of install_files() and install_targets().
This is more modern and also avoids stripping of the first character
from user-specified destinations.
While at it, fix the default destinations reported in the bootstrap
help.
This converts the CMake license to a pure 3-clause OSI-approved BSD
License. We drop the previous license clause requiring modified
versions to be plainly marked. We also update the CMake copyright to
cover the full development time range.