cosmetics & warnings

- remove some unused functions
- move global arrays from data to read only section
- explicitly cast malloc returns; not specifically necessary, but helps
  show intent
- miscellaneous formatting

Change-Id: Ib15fe5b37fe6c29c369ad928bdc3a7290cd13c84

src/dsp/cpu.c

@@ -59,6 +59,7 @@ VP8CPUInfo VP8GetCPUInfo = x86CPUInfo;
 // define a dummy function to enable turning off NEON at runtime by setting
 // VP8DecGetCPUInfo = NULL
 static int armCPUInfo(CPUFeature feature) {
+  (void)feature;
   return 1;
 }
 VP8CPUInfo VP8GetCPUInfo = armCPUInfo;