Support for type dynamic in VM

Support for type dynamic in VM

Old name Dynamic is supported, and automatically converted to
lower-case dynamic when parsed.

VM flag --warn_legacy_dynamic prints warnings when Dynamic
is found.
Committed: https://code.google.com/p/dart/source/detail?r=13637

[hausner, 2012-10-12 20:05:25]

It's actually a small change, mostly changes in comments.

[regis, 2012-10-12 20:52:12]

LGTM, but since dart2js already supports dynamic, why not fix all the language
tests as part of this cl?

[hausner, 2012-10-12 21:58:58]

Done. Will do another round of testing before checkin. Thank you.