swift234

PerformanceInliner: Improve the inlining heuristic to reduce code size.

It now detects more opportunities for inlining, like some patters with RC instructions or loads/stores from/to stack locations in the caller.
On the other hand a new shortest path analysis limits inlining to those cases where it really gives a benefit.

As the inlining decision now depends on many parameters, the test-threshhold option is removed because it doe not make much sense anymore.
Instead the inliner test files are modified to model the "real" instruction costs.