These checks are necessary cause of a recent change in the C++ engine.

Reviewed-by: Roberto Raggi

The helpId was working but the tooltip text was empty.

Reviewed-by: Roberto

RevBy: Roberto

In some projects these kind of files are used for completely inlined
classes, that can be split up in a header and source file automatically.

Details:
This patch makes use of system icons as a base
and draws overlay on top. This should blend a bit better
into the native icon theme.

Many singletons have their own instance() method, in which case there is
no need to use ICore::instance() to get access to them.

there anymore

replace ExtensionSystem::PluginManager::instance()->getObject<Core::ICore>() by Core::ICore::instance()

forward declaration is sufficient.

Details:  - Naming convention

Details:  - Conform to naming convention

Details:  - To make it conform to naming convention.

The overview combo in the toolbar above the editor traditionally liked
to be rather small. Now it will prefer to expand.

Details:  in all pluginspecs.

Necessary because the CppHoverHandler uses QtHelp and moved from
CppTools to CppEditor.

Lowercase is the more prevalent style in this plugin and CppTools.
Unfortunately CPPEditor can't be named CppEditor cause of the CppEditor
namespace.

It used to be in CppTools, but since the hover handler only makes sense
in the context of the C++ editor, this is a better place.

This change removes a number of wrong usages of the CppModelManager::documents()/document().

when opening files from the C++ editor (e.g. when the user press F2 on #include <QMutex>).