Disable all warnings seen on devkitA64 GCC 15.1.0:

- Several false-positive `-Wmisleading-indentation` warnings (the
  indentation is not actually misleading)

- One `-Wuse-after-free` warning, which looks alarming and represents
  very dubious design, but is ultimately harmless (a freed pointer is
  passed to a function that doesn't use it).

- Some `-Wunused-function` warnings in `simd/neon.h`