Vc::abs: only for double, float, int, and short

The Vc::abs function now ensures it is only visible for floating point
types and signed integral types. This is in line with std::abs behavior.

Signed-off-by: Matthias Kretz <kretz@kde.org>
mask: add public member typedefs

EntryType, VectorEntryType, and VectorType are also useful typedefs for
Mask types. This makes masks more useful in generic contexts.

Signed-off-by: Matthias Kretz <kretz@kde.org>
Vector: apply clang-format

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