[inliner] Print out extra stats about the cost, threshold, and vector
bonus in the inline cost analysis.

Split out of a patch by Dario Domizioli to commit separately.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200586 91177308-0d34-0410-b5e6-96231b3b80d8