First stab at JSON support.
Merge branch 'master' of https://github.com/mozilla/shumway
Only use non-refixed keys for integers.

This appears to work now but is most likely broken, so more work is needed here.
Fake out TextLineMetrics, to make GIRP to work.
Merge pull request #806 from mbebenita/master

JSON fixes and makes GIRP sort of work.