Look through PseudoObjectExpr and OpaqueValueExprs when scanning for
release-like operations. This commit also adds additional tests in anticipation
of re-writing this as a path-sensitive checker.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@260608 91177308-0d34-0410-b5e6-96231b3b80d8