This is important in case the data aren't owned by the instance but
instead referencing something else, for example the importer, a
memory-mapped file or another instance. Will get increasingly
important for zero-copy data import.
It limits the support for CMake 3.12+, but it's much less verbose and I
don't expect people to use ancient CMake versions with IDEs like Xcode
or VS anyway, so this should be fine.
Only the double ones, exposed as floats, because the extra ALU required
by doubles is negligible to function call overhead. It'll be different
for non-scalar types, but here I use this.
Vladimír Vondruš