vp8/common/variance*: add vp8_rtcd include

silences missing prototype warnings

Change-Id: I5ca198b56a5ff0cf5b93c89957526f243c04e9c8

vp8/common/variance_c.c

@@ -9,8 +9,9 @@
  */
 
 
-#include "variance.h"
+#include "./vp8_rtcd.h"
 #include "filter.h"
+#include "variance.h"
 
 
 unsigned int vp8_get_mb_ss_c

vp8/common/x86/variance_mmx.c

@@ -8,6 +8,7 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
+#include "./vp8_rtcd.h"
 #include "vpx_config.h"
 #include "vp8/common/variance.h"
 #include "vpx_ports/mem.h"

vp8/common/x86/variance_sse2.c

@@ -8,6 +8,7 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
+#include "./vp8_rtcd.h"
 #include "vpx_config.h"
 #include "vp8/common/variance.h"
 #include "vpx_ports/mem.h"

vp8/common/x86/variance_ssse3.c

@@ -8,6 +8,7 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
+#include "./vp8_rtcd.h"
 #include "vpx_config.h"
 #include "vp8/common/variance.h"
 #include "vpx_ports/mem.h"