Use configure checks for various inline keywords.

Change-Id: I8508f1a3d3430f998bb9295f849e88e626a52a24
diff --git a/vp9/common/vp9_common.h b/vp9/common/vp9_common.h
index 2e1ee4b..4295eba 100644
--- a/vp9/common/vp9_common.h
+++ b/vp9/common/vp9_common.h
@@ -42,7 +42,7 @@
 
 #define vp9_zero_array(Dest, N) vpx_memset(Dest, 0, N * sizeof(*Dest));
 
-static __inline uint8_t clip_pixel(int val) {
+static INLINE uint8_t clip_pixel(int val) {
   return (val > 255) ? 255u : (val < 0) ? 0u : val;
 }