Fix static name resolution in mixing code

Fix static name resolution in mixing code

In mixin code, static names need to be looked up in the mixin class.
OTOH, in patch classes, we need to resolve static names in the
class into with the code is patched. I'm all for simplicity!

TBR=iposva

Committed: https://code.google.com/p/dart/source/detail?r=18710

[hausner, 2013-02-19 18:27:28]

TBR

[Ivan Posva, 2013-02-19 19:04:29]

LGTM -ip