Revert commit f84af8e270 (add_test: Allow special characters in test
name, 2020-05-16, v3.18.0-rc1~142^2). Unfortunately the fix breaks
projects that were working around the limitation with manual escaping.
The fix can be re-introduced with a policy in a future version.
Also add a 3.18.1 release note explaining the change.
Fixes: #21017, #20965
Issue: #19391
Add a `COMMAND_EXPAND_LISTS` option to the `add_test` command to cause
`;`-separated lists produced by generator expressions to be expanded
into multiple arguments. The `add_custom_command` command already
has such an option.
Fixes: #17284
Generator expressions are supported in many places and are a distinct
concept worthy of their own manual page. The old builtin documentation
was previously represented by preprocessor macros to generate it into
each place that supports them. Factor out the duplicate content into a
dedicated cmake-generator-expressions manual page and reference it from
each original location.