Remove altivec.h header?

[mardy]

Hi! I'm not sure that this is a bug in devkitPPC itself, but maybe you won't be against making a workaround in devkitPPC (or maybe you'll be able to give me a better suggestion).

As I understand from here, the powerpc processor on the Wii and Gamecube does not support the altivec instruction set. Yet, when I build libSDL2, it gets enabled, because this program compiles successfully on devkitPPC (source):

      check_c_source_compiles("
          #include <altivec.h>
          vector unsigned int vzero() {
              return vec_splat_u32(0);
          }
          int main(int argc, char **argv) { return 0; }" HAVE_ALTIVEC_H_HDR)
      check_c_source_compiles("
          vector unsigned int vzero() {
              return vec_splat_u32(0);
          }
          int main(int argc, char **argv) { return 0; }" CPU_SUPPORTS_ALTIVEC)

For the time being, I've manually disabled this check when building for the GameCube/Wii, but it would be nicer if I didn't have to do that.

[WinterMute]

Linking to stuff I said 15 years ago isn't even slightly fair :P

Setting CPU_SUPPORTS_ALTIVEC purely on the existence of the altivec header seems a bit wrong tbh. I'm not averse to removing it fron devkitPPC though.

We have a few things in progress right now though so it will likely be in the new year when we look at newlib updates.