Doesn't use them in libc headers so that those don't have to pull in
AK/Platform.h.
AK_COMPILER_GCC is set _only_ for gcc, not for clang too. (__GNUC__ is
defined in clang builds as well.) Using AK_COMPILER_GCC simplifies
things some.
AK_COMPILER_CLANG isn't as much of a win, other than that it's
consistent with AK_COMPILER_GCC.
Clang didn't accept the friend declaration here, as the class has a
requires clause attached to it, and I couldn't immediately figure
out what it wants instead.
Add accessors for VectorN::m_data and use those where needed instead
for now.
`Gfx::Vector[2,3,4]` are nearly identical implementations. This code
redundancy does not follow the DRY (Don't Repeat Yourself) principle
leading to possible out-of-sync errors between the classes.
Combining these classes into a class template which can be specialized
for each needed size makes the differences obvious through
`constexpr-if` blocks and `requires` clauses.
