Storage: declare BuiltinType::type default
Storage: declare BuiltinType::type default

The default is needed in SFINAE contexts that would otherwise lead to
ill-formed programs.

Signed-off-by: Matthias Kretz <372ea4eca737a13cd010ee806d4ce7b98ee71550@kde.org>

VcDevel/Vc,VcDevel/Vc,chr-engwer/Vc,VcDevel/Vc,VcDevel/Vc,chr-engwer/Vc,chr-engwer/Vc