Implement Gesture API

This is by no means complete, but it's a start.
@andreasgal was previously apprehensive about modifying the reference implementation files. Perhaps we should copy these files to another class hierarchy that overrides the reference implementation, i.e. a java/something/ hierarchy that overrides same-named classes in java/cldc1.1.1/ and java/midp/. Then we can compare our files to the reference implementation versions at any time simply by diffing the hierarchies.