change the objectsize intrinsic signature: add a 3rd parameter to denote the maximum...

change the objectsize intrinsic signature: add a 3rd parameter to denote the maximum runtime performance penalty that the user is willing to accept.
This commit only adds the parameter. Code taking advantage of it will follow.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@156473 91177308-0d34-0410-b5e6-96231b3b80d8