Revert "[analyzer; alternate edges] improve support for edges with PseudoObjectExprs."

Ted and I spent a long time discussing this today and found out that neither
the existing code nor the new code was doing what either of us thought it
was, which is never good. The good news is we found a much simpler way to
fix the motivating test case (an ObjCSubscriptExpr).

This reverts r182083, but pieces of it will come back in subsequent commits.

llvm-svn: 182185