ICC: work around C++ frontend issues
ICC: work around C++ frontend issues

ICC messes up overload resolution and SFINAE. Luckily there are many
ways to express my intent and one of them works with ICC, too. IIC still
fails to implement the is_constructible_with_double_brace and
is_constructible_with_single_brace traits, though.

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

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