PR17052 / DR1560 (+DR1550): In a conditional expression between a glvalue and a
throw-expression, the result is also a glvalue and isn't unnecessarily coerced
to a prvalue.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@200189 91177308-0d34-0410-b5e6-96231b3b80d8