Fix bug where sys::Wait could wait on wrong pid.

Setting ChildPid to -1 would cause waitpid to wait for any child process.

Patch by Daniel Reynaud!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220717 91177308-0d34-0410-b5e6-96231b3b80d8
[ScalarEvolution] Guard dump() with #if

to be consistent with its definition in ScalarEvolution.cpp


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220721 91177308-0d34-0410-b5e6-96231b3b80d8