New code assist API

This is a re-work of our completion engine. Primary goals are:

- Allow the computation to run in a separate thread so the GUI is not locked.
- Support a model-based approach. QStrings are still needed (filtering, etc), but
internal structures are free to use more efficient representations.
- Unifiy all kinds of *assist* into a more reusable and extensible framework.
- Remove unnecessary dependencies on the text editor so we have more generic
and easily "plugable" components (still things to be resolved).

src/plugins/texteditor/codeassist/iassistprovider.cpp

@@ -0,0 +1,68 @@
+/**************************************************************************
+**
+** This file is part of Qt Creator
+**
+** Copyright (c) 2011 Nokia Corporation and/or its subsidiary(-ies).
+**
+** Contact: Nokia Corporation (info@qt.nokia.com)
+**
+**
+** GNU Lesser General Public License Usage
+**
+** This file may be used under the terms of the GNU Lesser General Public
+** License version 2.1 as published by the Free Software Foundation and
+** appearing in the file LICENSE.LGPL included in the packaging of this file.
+** Please review the following information to ensure the GNU Lesser General
+** Public License version 2.1 requirements will be met:
+** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain additional
+** rights. These rights are described in the Nokia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** Other Usage
+**
+** Alternatively, this file may be used in accordance with the terms and
+** conditions contained in a signed written agreement between you and Nokia.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at info@qt.nokia.com.
+**
+**************************************************************************/
+
+#include "iassistprovider.h"
+
+using namespace TextEditor;
+
+/*!
+    \class IAssistProvider
+    \brief The IAssistProvider is an interface for providing code assist.
+
+    There might be different kinds of assist such as completions or refactoring
+    actions (quickfixes).
+
+    Within this API the term completion denotes any kind of information prompted
+    to the user in order to auxiliate her to "complete" a particular code construction.
+    Examples of completions currently supported are snippets, function hints, and
+    contextual contents.
+
+    \sa IAssistProposal, IAssistProcessor
+*/
+
+IAssistProvider::IAssistProvider()
+{}
+
+IAssistProvider::~IAssistProvider()
+{}
+
+/*!
+    \fn bool supportsEditor(const QString &editorId) const
+
+    Returns whether this provider supports the editor which has the give \a editorId.
+*/
+
+/*!
+    \fn IAssistProcessor *createProcessor() const
+
+    Creates and returns the IAssistProcessor responsible for computing an IAssistProposal.
+*/