All the functionality is moved to Math::swizzle() and the result is
casted to given type only if its header is included. Thus it is possible
to remove include dependency on Color. The original swizzle() is now
just an alias marked as deprecated and will be removed in future
release.
Also fixed unary RectangularMatrix::operator-() and Vector::operator-()
documentation (was stating that the operation is done in-place, which is
impossible.
They aren't much useful in Math namespace and here it allows to handle
also Color3/Color4 types. Moreover all RGBA component names were removed
from Math namespace, so it would be inconsistent to have them there only
in swizzle() functions.
On the other hand everything of this is done at runtime, so it's less
performant than the previous version, mainly when used in loops. When
the result is declared as constexpr, it is done at compile time, just
like the previous version.
I don't know which version to keep, so there will be both until a good
decision.
Vladimír Vondruš