Describe "Reset warnings" button

Disable the button if no warnings are suppressed

Task-number: QTCREATORBUG-8875
Change-Id: If019550eaf8e8745a506b512d206a2b0fd34dfeb
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/plugins/coreplugin/infobar.cpp

@@ -152,6 +152,11 @@ void InfoBar::clearGloballySuppressed()
     ICore::settings()->setValue(QLatin1String(C_SUPPRESSED_WARNINGS), QStringList());
 }
 
+bool InfoBar::anyGloballySuppressed()
+{
+    return !globallySuppressed.isEmpty();
+}
+
 
 InfoBarDisplay::InfoBarDisplay(QObject *parent)
     : QObject(parent)