When hovering over a C++ token that we have a man page for, we now show
the man page in a tooltip window.
This feels rather bulky at the moment, but the basic mechanism is quite
neat and just needs a bunch of tuning.
This patch adds Editor (subclass of GTextEditor) and EditorWrapper.
An EditorWrapper is a composite widget that adds a little statusbar
above an Editor widget. The statusbar is used for showing the filename
and the current cursor position. More things can definitely be added.
To get to the currently active editor, call current_editor().
You can also get to the current editor's wrapper by calling..
current_editor_wrapper(). Which editor is current is determined by
which was was last focused by the user.
