[analyzer] Simplify RetainCountChecker's handling of dead symbols.

Previously we made three passes over the set of dead symbols, and removed
them from the state /twice/. Now we combine the autorelease pass and the
symbol death pass, and only have to remove the bindings for the symbols
that leaked.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@169527 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed