Try to fix GCC warnings again

modules/ximgproc/perf/perf_precomp.hpp

@@ -1,6 +1,3 @@
-#ifndef __OPENCV_PERF_PRECOMP_HPP__
-#define __OPENCV_PERF_PRECOMP_HPP__
-
 #ifdef __GNUC__
 #  pragma GCC diagnostic ignored "-Wmissing-declarations"
 #  if defined __clang__ || defined __APPLE__
@@ -9,6 +6,9 @@
 #  endif
 #endif
 
+#ifndef __OPENCV_PERF_PRECOMP_HPP__
+#define __OPENCV_PERF_PRECOMP_HPP__
+
 #include <opencv2/ts.hpp>
 #include <opencv2/imgproc.hpp>
 #include <opencv2/highgui.hpp>

modules/ximgproc/test/test_precomp.hpp

@@ -1,6 +1,3 @@
-#ifndef __OPENCV_TEST_PRECOMP_HPP__
-#define __OPENCV_TEST_PRECOMP_HPP__
-
 #ifdef __GNUC__
 #  pragma GCC diagnostic ignored "-Wmissing-declarations"
 #  if defined __clang__ || defined __APPLE__
@@ -9,6 +6,9 @@
 #  endif
 #endif
 
+#ifndef __OPENCV_TEST_PRECOMP_HPP__
+#define __OPENCV_TEST_PRECOMP_HPP__
+
 #include <opencv2/ts.hpp>
 #include <opencv2/ts/ts_perf.hpp>
 #include <opencv2/core.hpp>