Support for new operator -

Support for new operator -

Implement unary operator -. Operator negate is still recognized,
but internally it is represented like unary -. In particular,
operator negate no longer implies an instance method named
negate.

Marked several co19 tests that use "negate" as failing and filed
co19 issue 169 to have these tests updated.
Committed: https://code.google.com/p/dart/source/detail?r=10523

[srdjan, 2012-08-10 00:11:32]

lgtm