CMake: harvest definitions in modules

[yurikhan]

Feature request

Summary

The CMake documentation includes pages describing bundled modules. DevDocs has an index entry for each module (e.g. CMakeDependentOption), but not for each entity defined within (e.g. cmake_dependent_option macro).

Harvesting these would improve search user experience, especially when using the technique described in the user guide under Prefilling the search field.

NB to implementor: a module can define more than one item and I’m not sure the markup is consistent between module doc pages.