Qt4: don't require a X server in the tests

Issue #5069

(cherry picked from commit 927a8b5071a8ee360ea4a1b24d093d8e9acacf18 and
a4310f0f5c4855c5249ffb1355c6fc039e141316)

test/testchecksumvalidator.cpp

@@ -151,7 +151,13 @@ using namespace OCC;
 };
 
 #if QT_VERSION < QT_VERSION_CHECK(5, 0, 0)
-    QTEST_MAIN(TestChecksumValidator)
+// Qt4 does not have QTEST_GUILESS_MAIN, so we simulate it.
+int main(int argc, char *argv[])
+{
+    QCoreApplication app(argc, argv);
+    TestChecksumValidator tc;
+    return QTest::qExec(&tc, argc, argv);
+}
 #else
     QTEST_GUILESS_MAIN(TestChecksumValidator)
 #endif

test/testfolderwatcher.cpp

@@ -171,7 +171,13 @@ private slots:
 };
 
 #if QT_VERSION < QT_VERSION_CHECK(5, 0, 0)
-    QTEST_MAIN(TestFolderWatcher)
+// Qt4 does not have QTEST_GUILESS_MAIN, so we simulate it.
+int main(int argc, char *argv[])
+{
+    QCoreApplication app(argc, argv);
+    TestFolderWatcher tc;
+    return QTest::qExec(&tc, argc, argv);
+}
 #else
     QTEST_GUILESS_MAIN(TestFolderWatcher)
 #endif

test/testxmlparse.cpp

@@ -442,7 +442,13 @@ private slots:
 };
 
 #if QT_VERSION < QT_VERSION_CHECK(5, 0, 0)
-    QTEST_MAIN(TestXmlParse)
+// Qt4 does not have QTEST_GUILESS_MAIN, so we simulate it.
+int main(int argc, char *argv[])
+{
+    QCoreApplication app(argc, argv);
+    TestXmlParse tc;
+    return QTest::qExec(&tc, argc, argv);
+}
 #else
     QTEST_GUILESS_MAIN(TestXmlParse)
 #endif