Some requirement machine work
Rename requirement to Value
Rename more things to Value
Fix integer checking for requirement
some docs and parser changes
Minor fixes
Although I don't plan to bring over new assertions wholesale
into the current qualification branch, it's entirely possible
that various minor changes in main will use the new assertions;
having this basic support in the release branch will simplify that.
(This is why I'm adding the includes as a separate pass from
rewriting the individual assertions)
Also, store the end location of the where clause explicitly, so that
we can recover it even if there are no requirements.
This fixes one of the failing tests when parser lookup is disabled in
swift-ide-test by ensuring that the source range of the function
extends to the end of the 'where' clause, even though the 'where'
clause has a code completion token in it.
