clang-format: Fix special case of binary operator detection.

There is a pattern where evaluation order is used as control flow.
This patch special-cases a commonly occuring version of this pattern.

Before:
  Aaaaa *aaa = nullptr;
  // ...
  aaa &&aaa->f();

After:
  Aaaaa *aaa = nullptr;
  // ...
  aaa && aaa->f();

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@210017 91177308-0d34-0410-b5e6-96231b3b80d8