C++0x scoped enums don't implicitly convert to an integral type, so we 
need to be careful about throwing away explicit conversions.  In this 
case, the static_cast<int>(e) creates a NOP_EXPR which get_narrower 
throws away, but 'e' itself is not a valid argument for &, so we need to 
replace the NOP_EXPR with a different one.

Tested x86_64-pc-linux-gnu.  OK for trunk?