libvpx: Add VP9 decoder.

source/libvpx/vpx_scale/vpx_scale_rtcd.sh

+vpx_scale_forward_decls() {
+cat <<EOF
+struct yv12_buffer_config;
+EOF
+}
+forward_decls vpx_scale_forward_decls
+
+# Scaler functions
+if [ "CONFIG_SPATIAL_RESAMPLING" != "yes" ]; then
+    prototype void vp8_horizontal_line_5_4_scale "const unsigned char *source, unsigned int source_width, unsigned char *dest, unsigned int dest_width"
+    prototype void vp8_vertical_band_5_4_scale "unsigned char *source, unsigned int src_pitch, unsigned char *dest, unsigned int dest_pitch, unsigned int dest_width"
+    prototype void vp8_horizontal_line_5_3_scale "const unsigned char *source, unsigned int source_width, unsigned char *dest, unsigned int dest_width"
+    prototype void vp8_vertical_band_5_3_scale "unsigned char *source, unsigned int src_pitch, unsigned char *dest, unsigned int dest_pitch, unsigned int dest_width"
+    prototype void vp8_horizontal_line_2_1_scale "const unsigned char *source, unsigned int source_width, unsigned char *dest, unsigned int dest_width"
+    prototype void vp8_vertical_band_2_1_scale "unsigned char *source, unsigned int src_pitch, unsigned char *dest, unsigned int dest_pitch, unsigned int dest_width"
+    prototype void vp8_vertical_band_2_1_scale_i "unsigned char *source, unsigned int src_pitch, unsigned char *dest, unsigned int dest_pitch, unsigned int dest_width"
+fi
+
+prototype void vp8_yv12_extend_frame_borders "struct yv12_buffer_config *ybf"
+specialize vp8_yv12_extend_frame_borders neon
+
+prototype void vp8_yv12_copy_frame "struct yv12_buffer_config *src_ybc, struct yv12_buffer_config *dst_ybc"
+specialize vp8_yv12_copy_frame neon
+
+prototype void vp8_yv12_copy_y "struct yv12_buffer_config *src_ybc, struct yv12_buffer_config *dst_ybc"
+specialize vp8_yv12_copy_y neon