6684385: Loop unswitching crashes without LoopNode
Summary: Without LoopNode, exit early from loop unswitching and partial peeling
Reviewed-by: kvn, never, sgoldman
6603919: Stackwalking crash on x86 -server with Sun Studio's collect -j on
Summary: Rewrite frame::safe_for_sender and friends to be safe for collector/analyzer
Reviewed-by: dcubed, kvn