our UNUSED macro is essentially a no-op for MSVC, which lead to
the situation where this well meant macro was emitting the
following warning:
C4189: 'UNUSED_i': local variable is initialized but not referenced
However since we have been on c++17 for a while now the UNUSED
macro can be replaced with the standard [[maybe_unused]] attribute
in cpp files.
This changes cleans up the use of the UNUSED macro in the
bf_nodes_geometry project.
Differential Revision: https://developer.blender.org/D12915
Reviewed by: JacquesLucke, Severin, Sergey, HooglyBoogly
e95b4dc2dd