CorePlugin: Compile with QT_NO_CAST_FROM_ASCII.

- Wrap literals in QLatin1String()/QLatin1Char().
- Extract some string constants avoiding repeated
  QString construction.
- Fix repeated invocation of Container.end() in loops.

Change-Id: If737735507aaf82e53063adda53f54c46418f42f
Reviewed-by: Tobias Hunger <tobias.hunger@nokia.com>

src/plugins/coreplugin/progressmanager/futureprogress.cpp

@@ -216,7 +216,7 @@ void FutureProgress::cancel()
 
 void FutureProgress::updateToolTip(const QString &text)
 {
-    setToolTip("<b>" + title() + "</b><br>" + text);
+    setToolTip(QLatin1String("<b>") + title() + QLatin1String("</b><br>") + text);
 }
 
 void FutureProgress::setStarted()