- Unexport Core::Internal::MainWindow and remove its includes.
- Move RssFetcher from Core::Internal to Core.
- Unexport CopyTaskHandler.
- Move TextEditor's completion support and Refactor Overlay
  helper classes from TextEditor::Internal to TextEditor as they
  are exported.
- Move internal BaseTextBlockSelection into private header.
- Unexport TextEditorOverlay as they are not used.

There was an off-by-one error for the normal find scope.
Improved look by ignoring the left side.

There was an off-by-one error for the normal find scope.
Improved look by ignoring the left side.

Task-number: QTCREATORBUG-2099
Reviewed-by: mae

Done-with: Roberto Raggi

Block selection was "broken" when using tabs, or rather
incomplete: It treated tabs as normal characters, which
has shown to be unexpected by people using tabs in code.

The new implementation has a vastly improved find scope
as well. In addition, creating a blog selection with
mouse or keyboard feels a lot more solid now, as the
actual selection is detached from possible valid cursor
positions.

Task-number: QTCREATORBUG-1541

Fixes the performance of large find scope selections. Try
Ctrl+A Ctrl+F in a large file and scroll.

The Parentheses, TextBlockUserData and TextEditDocumentLayout classes
and their member function implementations were spread around the
BaseTextEditor class. Moving them to their own file to make the code a
bit better organized.

Reviewed-by: mae

If the first or last line in a selection ended up with nothing to
highlight after whitespaces were trimmed, they'd use a codepath that
only works correctly for inner 'empty' lines.

Instead we now make sure the beginning and end of a selection are always
highlighted.

Done with: mae

the new approach makes it possible to use more edit features
inside the rename selection like cut/copy/paste. Furthermore
it compresses rename operations better on the undo stack.

done with thorbjorn

done with thorbjorn

Remove overlap. Add extra selection tooltips for the cpp hover handler.

1. allow empty overlay selections
2. make it possible to bind a selection to a specified length

As side effect we can now play a bit with visualizing extra selections