Update analyzer to reflect new rules for prefixes.

Update analyzer to reflect new rules for prefixes.

As of commit 67b99e4b33023ecf162148fb8400da8839d73065, it is now
consistently a compile error for a prefix not to be followed by '.'.
(Previously, there were two exceptions in which a prefix not followed
by '.' was treated as though it was preceded by "this.")

This CL updates analyzer to be consistent with the new spec langauge,
and modifies the tests in tests/language accordingly.

Dart2js and the VM do not yet produce the correct compile-time error
in all circumstances.  See issues #23611 and #23612.

R=brianwilkerson@google.com

Committed: https://github.com/dart-lang/sdk/commit/9c90a66d0d9f2dd6f3e7cd831f2a3e15ddeb8603

[Paul Berry, 2015-06-17 21:50:23]

paulberry@google.com changed reviewers:
+ brianwilkerson@google.com

[Brian Wilkerson, 2015-06-17 22:20:45]

LGTM

[Paul Berry, 2015-06-18 17:03:10]

Committed patchset #1 (id:1) manually as
9c90a66d0d9f2dd6f3e7cd831f2a3e15ddeb8603 (presubmit successful).