The COMPILE_DEFINITIONS escaping disclaimer was represented in builtin
documentation using a preprocessor macro. Factor the duplicate content
out into a separate .txt file and include it in each document with the
reStructuredText include directive.
These documents were represented in the builtin documentation using a
common starting point with placeholders substituted by each command.
Convert them back to this approach using the reStructuredText include
directive and substitutions to avoid duplication.
Portions of these documents contain duplicate content generated from
preprocessor macros in the original builtin documentation source.
Factor the common parts out into .txt files using reStructuredText
include directives and substitutions to avoid duplication.
Add a top-level document holding the Sphinx root toctree. List all
reference manuals from Help/manual/*.rst and the Sphinx-generated
general index (genindex) and search pages.
Run "cmake --help-full cmake.1.rst" by hand on Windows and OS X.
Copy the generator/*.rst documents for generators unique to those
platforms into Help/generator.
