QtCore: fix the number precision in QJsonDocument.toJson() again

Need to store 17 decimal digits for binary64, IEEE 754 double formats.

Autotest is included. Test cases from TC39 test suite for ECMAScript.

Task-number: QTBUG-31926
Change-Id: I546398f21ea7ff5e40e89fc9de8703f628f55df9
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@digia.com>
benchmarks: Re-enable QFileInfo build by removing canonicalFileNamePerformance.

QFSFileEnginePrivate::canonicalized has been gone for a very, very long time now
(since d3b152ba1e3cd38dd675c801474105d518bacb44 in Qt 4).

This also fixes a build failure in the code on Windows.

Change-Id: I81f5e0c1d644b1b4d75644626eb394a663535387
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Stabilize tst_QApplication::quitOnLastWindowClosed().

Instantiate widgets on the stack to ensure they are destroyed
when the QApplication instance goes out of scope.
Introduce waitForWindowExposed() to make sure events are in sync.

Task-number: QTBUG-32125
Change-Id: Ia54e2fa9a7c2e279353c4514a6735e326edf35ae
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>
Fix crash caused by ~QWindowsWindow flushing the event queue.

Remove call to QWindowSystemInterface::flushWindowSystemEvents()
introduced by 153d613353863987322db81f3c31e33541ef7226 .

Task-number: QTBUG-32125

Change-Id: I14aa2772848e04b47deff6218b48eaf69f0bb649
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>
don't crash if builddir is suffix of sourcedir (or vice-versa)

Task-number: QTBUG-32145
Change-Id: I97a6e2ebd51350cbf39c86efa5c26a376c49da95
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
VPATH resolution: don't crash when $(FOO) expands to nothing

Task-number: QTBUG-29988
Change-Id: Ice3dc28002fc70e70fecc5d61bd0b32260ac0d50
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
merge string literals

makes for less visual noise and a tiny bit more efficient code.

Change-Id: I587707fa4e2dc9bead9435bf5caf3a98ab680725
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@digia.com>
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
doc: Build fix to QSettings documentation snippets.

The constructor taking a global color was removed in Qt 5.0.0.
We need to explicitly convert to QColor before we get a QVariant.

Change-Id: I821f164b8601647b062eeef57372755fa187c50c
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>