Partially needed to avoid build breakages because Corrade itself
switched as well, partially because a cleanup is always good. Done
except for (STL-heavy) code that's deprecated or SceneGraph-related APIs
that are still quite full of STL as well.
Merging two sorted sequences is is something I always struggle with to
write from scratch. Fortunately here I could just reuse what got done for
DebugTools::CompareMaterial already, haha.
Such an unnecessary footgun -- I was already checking the other case,
having attribute data too short, but this I thought is fine because it's
not leading to any crash. Well it's leading to needless pain and
suffering, that's what it is doing!
And of course already found FIVE such bugs in just Magnum tests alone.
Currently contains just one very silly Phong->PBR conversion utility,
but eventually it'll provide tools for simplifying, merging and
deduplicating materials.