Lemon fix: incorrect printf format strings.

Updated lemon to the latest in my fossil repo. My assumption is that many of my __MOJOSHADER__ blocks will be formal parts of upstream Lemon, so I've merged over for now, removing the #ifdefs where appropriate. I'm keeping %expect support for now, even though drh didn't like the idea, since I can't wrap my stupid head around the parser conflict resolution process yet.

Lemon now writes errors to stderr instead of stdout, and uses full output. The previous way truncated the filename, so my editor couldn't jump to the problem line in the source code.

Lemon now deletes its output on failure. This is to fix the build system. Previously, a Makefile would abort when lemon fails, but on the next run it would see a newer (incorrect/incomplete) output file, and assume it succeeded previously, with disastrous effects for later steps in the build process.

Merged calculator-experiment back into default branch.

Moved the calculator experiment work back into the compiler. At least we know the expression parser works! :) Lots of other bits of new infrastructure in there, too.

Don't pass the TokenData back out of the lemon code.

Removed some Context fields we don't really need.

"identifier" shouldn't be a non-terminal.

Cleaned up TokenData FIXMEs, and added string cache.