Revise docs for all "Scripting Commands", except four find_XXX
that use a macro suite of their own.
* Take full advantage of the improved syntax highlighting.
* Make consequential use of <..> placeholders.
* Clarify things here and there in the text.
Specific improvements to some command docs:
* "math": Correct description of novel hexadecimal capability.
* "if", "foreach", "while": Provide link to "endif" etc
* "foreach", "while": Mention "break" and "continue".
* "foreach": Simplify explanation of ``RANGE`` and ``IN`` signatures;
advise against negative arguments or reverse ranges (compare issue #18461)
* "endif", "endfunction" etc: Explain that the argument is optional and
maintained for compatibility only
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
