Add `SpriteLoader::SpriteCollection` type which is an array of `SpriteLoad::Sprite`.
This removes the ambiguity of what `SpriteLoader::Sprite *` is pointing to,
and cleans up mismatches using both dereference -> and array access [] for the
same object.
This is the only enumeration with a COUNT and END. The logic of the COUNT
implied that BEGIN could be non-zero, but all but two uses of zoom level
assume that BEGIN is zero, making the separate count only confusing.
This is a C++11 feature that allows the compiler to check that a virtual
member declaration overrides a base-class member with the same signature.
Also src/blitter/32bpp_anim_sse4.hpp +38 is no longer erroneously marked
as virtual despite being a template.
With 32bpp base set about 30% faster than 32bpp-optimized, or about 10% for 8bpp base sets in the Draw function. Respectively about 5 and 1% of total run time