Improve compile times for swarm application startup

Improve compile times for swarm application startup
- Avoid creation of getter/setter symbol when all we need to do is a lookup
- Add LookupGetterFunction/LookupSetterFunction to avoid having to create the getter name/setter name before doing a lookup
Committed: https://code.google.com/p/dart/source/detail?r=3453

[hausner, 2012-01-20 00:28:56]

LGTM

[siva, 2012-01-20 00:50:03]

Thanks.