LoopRotate: When reconstructing loop simplify form don't split edges
from indirectbrs.
Yet another chapter in the endless story. While this looks like we
leave the loop in a non-canonical state this replicates the logic in
LoopSimplify so it doesn't diverge from the canonical form in any way.
http://llvm.org/PR21968
This fixes a "Cannot split critical edge from IndirectBrInst" assertion
failure when building the devel/radare2 port.
PR: 195480, 196987
MFC after: 3 days
a6d980a99e