[SimplifyCFG] Extend TryToSimplifyUncondBranchFromEmptyBlock for empty block...

[SimplifyCFG] Extend TryToSimplifyUncondBranchFromEmptyBlock for empty block including lifetime intrinsics

Make it possible that TryToSimplifyUncondBranchFromEmptyBlock merges empty
basic block including lifetime intrinsics as well as phi nodes and
unconditional branch into its successor or predecessor(s).

If successor of empty block has single predecessor, all contents including
lifetime intrinsics are sinked into the successor. Otherwise, they are
hoisted into its predecessor(s) and then merged into the predecessor(s).

Patch by Josh Yoon <josh.yoon@samsung.com>!

Differential Revision: http://reviews.llvm.org/D19257

llvm-svn: 268254