test/idct_test: add missing vpx_integer.h include

Change-Id: I9de764638ec981bb34fc8e183985d8c285b006fb

test/idct_test.cc

diff --git a/test/idct_test.cc b/test/idct_test.cc
index ea61e0b..2c7fa0e 100644
--- a/test/idct_test.cc
+++ b/test/idct_test.cc
@@ -16,6 +16,8 @@
 #include "test/register_state_check.h"
 #include "third_party/googletest/src/include/gtest/gtest.h"
 
+#include "vpx/vpx_integer.h"
+
 typedef void (*idct_fn_t)(int16_t *input, unsigned char *pred_ptr,
                           int pred_stride, unsigned char *dst_ptr,
                           int dst_stride);