[analyzer] Run remove dead on end of path.

This will simplify checkers that need to register for leaks. Currently,
they have to register for both: check dead and check end of path.

I've modified the SymbolReaper to consider everything on the stack dead
if the input StackLocationContext is 0.

(This is a bit disruptive, so I'd like to flash out all the issues
asap.)

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@167352 91177308-0d34-0410-b5e6-96231b3b80d8
7 files changed