[analyzer] Fix a bad bug in reversePropagateInterstingSymbols() where only one subexpression of BinaryOperator would be explored.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@204374 91177308-0d34-0410-b5e6-96231b3b80d8
Remove dead assignment dominated by a call to llvm_unreachable().

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@204375 91177308-0d34-0410-b5e6-96231b3b80d8
[-Wunreachable-code] Tweak isTrivialDoWhile() to handle implicit casts.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@204376 91177308-0d34-0410-b5e6-96231b3b80d8