test: fixed tst_qundostack and removed CONFIG+=insignificant_test

This test had an invalid circular dependency: the test is in qtbase, and
it depends on lrelease in qttools, which depends on qtbase.

Change the test to skip if lrelease is not available or not working.

Change-Id: I4696f4a178a6f8c0f2e76b5c4ae7f60c4f953334
Reviewed-on: http://codereview.qt.nokia.com/2619
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Rohan McGovern <rohan.mcgovern@nokia.com>

tests/auto/qundostack/qundostack.pro

@@ -1,5 +1,3 @@
 CONFIG += qttest_p4
 SOURCES += tst_qundostack.cpp
 TARGET = tst_qundostack
-
-CONFIG+=insignificant_test

tests/auto/qundostack/tst_qundostack.cpp

@@ -2970,6 +2970,11 @@ void tst_QUndoStack::undoLimit()
 void tst_QUndoStack::commandTextFormat()
 {
     QString binDir = QLibraryInfo::location(QLibraryInfo::BinariesPath);
+
+    if (QProcess::execute(binDir + "/lrelease -version") != 0) {
+        QSKIP("lrelease is missing or broken", SkipAll);
+    }
+
     QVERIFY(!QProcess::execute(binDir + "/lrelease testdata/qundostack.ts"));
 
     QTranslator translator;