Remove PUB_SUGGESTION error type from analyzer.

Remove PUB_SUGGESTION error type from analyzer.

This error type is not currently used (the code to generate it is
still under development), and there is no corresponding error type in
the analysis server API.  It seems like it should be adequate to
classify these as hints.

R=brianwilkerson@google.com

Committed: https://code.google.com/p/dart/source/detail?r=41014

[Paul Berry, 2014-10-08 21:31:33]

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

[Brian Wilkerson, 2014-10-08 23:21:19]

LGTM

[Paul Berry, 2014-10-09 14:07:04]

Committed patchset #1 (id:1) manually as 41014 (presubmit successful).