Teach the inline cost analysis about calls that can be simplified and

how to propagate constants through insert and extract value
instructions.

With the recent improvements to instsimplify, this allows inline cost
analysis to constant fold through intrinsic functions, including notably
the with.overflow intrinsic math routines which often show up inside of
STL abstractions. This is yet another piece in the puzzle of breaking
down the code for:

  void f() {
    std::vector<int> v;
    v.push_back(1);
  }

But it still isn't enough. There are a pile of bugs in inline cost still
blocking this.

llvm-svn: 171195