Prefix all in-source references to libcps

[bretbrownjr]

Including

• Spell #include statements like cps/*.hpp
• Spell preprocessor definitions like CPS_*
• Made enumerated values lowercase instead of UPPERCASE to avoid collisions with preprocessor definitions from other projects.

Incidental Changes

To make this commit less awkward, some incidental design changes were scoped in, including adding a src/cps subdirectory along with meson.build files to describe that subdirectory in a more encapsulated way for the rest of the build configuration.

HAVE_UNREACHABLE was renamed to CPS_USE_BUILTIN_UNREACHABLE.

main was reimplemented to be a pass-through call to a new cps_config::run function. This added a namespace to the cps-config program itself that is distinct from the namespace for the cps library.

Incidental changes to include sorting, quoting, and spacing were added to make automated code formatters behave well with current include sorting and spelling patterns.

Updated some copyright notices.

Justification

This will better prepare the project to publish a libcps in the future, which will be desireable.

Specifically:

• These changes will avoid conflicts with other projects that might ship, for instance, a utils.hpp
• These changes will avoid collisions with other projects that might define a variable named unreachable.
• These changes will avoid collisins with other projects that might define preprocessor macros like SIMPLE.

[bretbrownjr]

@dcbaker This touches all the interesting files, so it will of course be a pain to rebase. I'm doing this now because I'll be travelling a lot in the coming weeks and it would be nice to get this refactoring out of the way before then. That will make it easier for me to juggle batches of PRs that don't step on one another.

[bretbrownjr]

Oops. I agree. I thought that was in my ignore file. I'll amend and update the commit.