clang-format: text following #if is likely an expression.

Before:
  #if AAAA &&BBBB

After:
  #if AAAA && BBBB

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@199713 91177308-0d34-0410-b5e6-96231b3b80d8