swift234

Teach bridgeFromObjectiveC to make use of the knownConditionallyBridgeFromObjectiveC/knownForceBridgeFromObjectiveC

If a conformance to _BridgedToObjectiveC is statically known, generate a more efficient code by using the newly introduced library functions for bridging casts.
This covers the cases arising from the source code, but does not cover any casts resulting from SIL optimizations. Those will be covered by the subsequent commit.

This change is to stay in CSApply for now. But the plan is to make the bridged casts optimization a guaranteed optimization. Once it is done, there is no need to lower the bridged casts in a special way inside Sema, because they all can be handled by the optimizer in a uniform way. This would apply to bridging of Error types too.

Swift SVN r27101