Add FileVerifier::isCFIProtected().

Add a CFI protection check that is implemented by building a graph and inspecting the output to deduce if the indirect CF instruction is CFI protected. Also added the output of this instruction to printIndirectInstructions().

Reviewers: vlad.tsyrklevich

Subscribers: llvm-commits, kcc, pcc, mgorny

Differential Revision: https://reviews.llvm.org/D38428

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@316610 91177308-0d34-0410-b5e6-96231b3b80d8