Covers almost all blocks containing actual code, except:
* Parsed-literal blocks can't be highlighted, including many command
summaries and substitution-heavy docs like find_... commands.
This is a Sphinx limitation.
* Code with errors, like CMP0049, DEPLOYMENT_ADDITIONAL_FILES,
DEPLOYMENT_REMOTE_DIRECTORY, @PACKAGE_INIT@ substitution in the
tutorial, bracket arguments/comments in cmake-language.7 and
cmake-developer.7.
* FindQt4 module, which needs reformatting.
Every policy's documentation has a paragraph on what version of CMake
introduced it, how to set the policy, and whether CMake warns if the
policy is not set. The wording of this paragraph has diverged across
policies over time. Factor the paragraph out into a standard advice
document included by every policy.
This lets AUTOMOC and AUTOUIC process GENERATED files which
used to be ignored before.
A new policy CMP0071 ensures that the old behavior of ignoring
GENERATED files is enabled when the CMake compatibility version
CMAKE_MINIMUM_REQUIRED is < 3.10.
Closes#16186
