Teach `cmake_minimum_required` and `cmake_policy(VERSION)` to support a
version range of the form `<min>[...<max>]`. Define this to mean that
version `<min>` is required, but known policies up to those introduced
by `<max>` will be set to `NEW`. This will allow projects to easily
specify a range of versions for which they have been updated.
Implementation indicates that at least two components of VERSION must
be specified (see Source/cmCMakeMinimumRequired.cxx.) Therefore the
minor version is not optional.
Many projects put their project() call first, but the actions taken
by this command can be influenced by policies and other information
set by a call to cmake_minimum_required. Document in each of these
two commands that cmake_minimum_required should be called first.
Suggested-by: Alan W. Irwin
