Add testcase for r188873: MCTextAtom boundaries.

Check that they are correctly computed if the last instruction is
larger than 1 byte.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188923 91177308-0d34-0410-b5e6-96231b3b80d8
Style cleanup following David's review for r188876.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188924 91177308-0d34-0410-b5e6-96231b3b80d8
MC CFG: Remap enough for data too, analoguous to r188873.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188925 91177308-0d34-0410-b5e6-96231b3b80d8