Scalar: ensure initialization

Since Vector() is defaulted, it needs the in-class initialization of
m_data to VectorType().

Signed-off-by: Matthias Kretz <kretz@kde.org>
simdarray: drop variable names that are unused

Since the purpose of these functions is to extract a single argument
from the parameter list, only one of the arguments needs to be named.

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