Some of our "cmake" code blocks do not use fully valid CMake syntax
because they have placeholders for human reference. Sphinx has
never been able to properly lex and highlight these, but now warns.
Fix each block's syntax or change to a non-cmake block as appropriate.
if(TEST TestNameThatExists) will return true if a test with the name
TestNameThatExists has been added with add_test. The syntax is similar
to if(TARGET TargetName). Since use of "TEST" as an argument to if()
could previously be interpreted as a non-keyword argument, add policy
CMP0064 to treat it as a keyword as NEW behavior.
Manually update reStructuredText formatting. Use a definition list
for the possible if() tests supported. Add inline literal markup
as appropriate. Also make minor wording tweaks to make it flow
better with the new markup.
Add notes about macro arguments in the foreach, if, and list commands.
Add a section to the macro command documentation explaining in detail
how macro arguments are not variables.
