[port] Remove MMX test altogether

The `_may_i_use_cpu_feature()` intrinsic is not available in MSVC, so
remove the whole check, which is only used during init to check for
CPU support for MMX instructions (which all modern intel CPUs support)
and MMX instructions are being removed from AVS anyway.

avs/vis_avs/main.cpp

@@ -196,17 +196,6 @@ static int init(struct winampVisModule* this_mod) {
     }
 #endif
 
-#ifndef NO_MMX
-    extern int is_mmx(void);
-    if (!is_mmx()) {
-        MessageBox(this_mod->hwndParent,
-                   "NO MMX SUPPORT FOUND - CANNOT RUN AVS - GET THE NON-MMX VERSION.",
-                   "AVS ERROR",
-                   MB_OK | MB_ICONSTOP);
-        return 1;
-    }
-#endif
-
 #ifdef WA3_COMPONENT
     strcat(g_path, "\\wacs\\data");
 #endif

avs/vis_avs/render.cpp

@@ -36,10 +36,6 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include "wa_ipc.h"
 #include "wnd.h"
 
-#include <immintrin.h>
-
-int is_mmx(void) { return _may_i_use_cpu_feature(_FEATURE_MMX); }
-
 void Render_Init() {
     timingInit();