Clang: Show help with F1 even if there is a diagnostic

...at that particular location.

For example, the code

     new QSignalMapper;

produced a deprecated warning with Qt 5.12 and F1 led to "No
documentation available" as the diagnostic was always prioritized.

Task-number: QTCREATORBUG-21686
Change-Id: Icf03000fb6b9de04e467e758da6167018d154a21
Reviewed-by: Marco Bubke <marco.bubke@qt.io>
Reviewed-by: Ivan Donchevskii <ivan.donchevskii@qt.io>
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/texteditor/basehoverhandler.cpp

@@ -73,6 +73,8 @@ void BaseHoverHandler::contextHelpId(TextEditorWidget *widget,
                                      int pos,
                                      const Core::IContext::HelpIdCallback &callback)
 {
+    m_isContextHelpRequest = true;
+
     // If the tooltip is visible and there is a help match, this match is used to update
     // the help id. Otherwise, let the identification process happen.
     if (!Utils::ToolTip::isVisible() || !lastHelpItemIdentified().isValid()) {
@@ -83,6 +85,8 @@ void BaseHoverHandler::contextHelpId(TextEditorWidget *widget,
     } else {
         propagateHelpId(widget, callback);
     }
+
+    m_isContextHelpRequest = false;
 }
 
 void BaseHoverHandler::setToolTip(const QString &tooltip)
@@ -105,6 +109,11 @@ const HelpItem &BaseHoverHandler::lastHelpItemIdentified() const
     return m_lastHelpItemIdentified;
 }
 
+bool BaseHoverHandler::isContextHelpRequest() const
+{
+    return m_isContextHelpRequest;
+}
+
 void BaseHoverHandler::propagateHelpId(TextEditorWidget *widget,
                                        const Core::IContext::HelpIdCallback &callback)
 {