QColor::colorNames(): reserve the result QStringList

Avoids reallocations.

Change-Id: I56afcdb400d1e07394e62a610f838a33feda9fe8
Reviewed-by: David Faure <david.faure@kdab.com>
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@digia.com>

src/gui/painting/qcolor_p.cpp

@@ -352,6 +352,7 @@ QStringList qt_get_colornames()
 {
     int i = 0;
     QStringList lst;
+    lst.reserve(rgbTblSize);
     for (i = 0; i < rgbTblSize; i++)
         lst << QLatin1String(rgbTbl[i].name);
     return lst;