Simplify template on inc-/decrement operators
Simplify template on inc-/decrement operators

Apple clang complains about the variadic template parameter on
operator++/-- (for no good reason, IMHO). Using a defaulted template
parameter should make this more portable, though.

Refs: gh-115
Signed-off-by: Matthias Kretz <372ea4eca737a13cd010ee806d4ce7b98ee71550@kde.org>

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