This reverts c79d1fa540390f6e37e1ea326153559eeadd0de6 and
125aa10b3d645bd26523a1bc321bb2e6b1cf04e1
Instead, use the previous approach but allow void-typed InitListExprs
with 0 initializers.
This happens for enum types with bool parent types. isBooleanType()
returns false for them however.
The previous version did the same thing by re-classifying the enum
integer type, but that breaks with forward-declared enums.
