Introduce codemodelbackend process and library

This is a partial result of wip/clang-oop. More will follow.

This allows us to invoke the completion out of the Qt Creator process
and thus safes us as against libclang crashes.

At this point only the completion use case is supported.

Some notes on the individual components:

 src/libs/codemodelbackendipc
  * library encapsulating the inter process communication handling
  * used by the backend application and in a follow-up change by the
    creator integration

 src/libs/3rdparty/sqlite
  * version 3.8.10.2
  * dependency of codemodelbackendipc, will be used to storage indexing
    data, among others

 src/tools/codemodelbackend
  * the backend application

 tests/unit:
  * unit tests

Change-Id: I91a48e27467581a22fb760a18d8eb926008fea60
Reviewed-by: Alessandro Portale <alessandro.portale@theqtcompany.com>
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@theqtcompany.com>
Reviewed-by: Marco Bubke <marco.bubke@theqtcompany.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>

src/libs/sqlite/sqlitedatabase.cpp

@@ -0,0 +1,146 @@
+/****************************************************************************
+**
+** Copyright (C) 2015 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing
+**
+** This file is part of Qt Creator.
+**
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and Digia.  For licensing terms and
+** conditions see http://www.qt.io/licensing.  For further information
+** use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 or version 3 as published by the Free
+** Software Foundation and appearing in the file LICENSE.LGPLv21 and
+** LICENSE.LGPLv3 included in the packaging of this file.  Please review the
+** following information to ensure the GNU Lesser General Public License
+** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
+** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Digia gives you certain additional
+** rights.  These rights are described in the Digia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+****************************************************************************/
+
+#include "sqlitedatabase.h"
+
+#include "sqlitetable.h"
+
+SqliteDatabase::SqliteDatabase()
+    : readDatabaseConnection(QStringLiteral("ReadWorker")),
+      writeDatabaseConnection(QStringLiteral("WriterWorker")),
+      journalMode_(JournalMode::Wal)
+{
+    connect(&readDatabaseConnection, &SqliteDatabaseConnectionProxy::connectionIsOpened, this, &SqliteDatabase::handleReadDatabaseConnectionIsOpened);
+    connect(&writeDatabaseConnection, &SqliteDatabaseConnectionProxy::connectionIsOpened, this, &SqliteDatabase::handleWriteDatabaseConnectionIsOpened);
+    connect(&readDatabaseConnection, &SqliteDatabaseConnectionProxy::connectionIsClosed, this, &SqliteDatabase::handleReadDatabaseConnectionIsClosed);
+    connect(&writeDatabaseConnection, &SqliteDatabaseConnectionProxy::connectionIsClosed, this, &SqliteDatabase::handleWriteDatabaseConnectionIsClosed);
+}
+
+SqliteDatabase::~SqliteDatabase()
+{
+    qDeleteAll(sqliteTables);
+}
+
+void SqliteDatabase::open()
+{
+    writeDatabaseConnection.setDatabaseFilePath(databaseFilePath());
+    writeDatabaseConnection.setJournalMode(journalMode());
+}
+
+void SqliteDatabase::close()
+{
+    writeDatabaseConnection.close();
+}
+
+bool SqliteDatabase::isOpen() const
+{
+    return readDatabaseConnection.isOpen() && writeDatabaseConnection.isOpen();
+}
+
+void SqliteDatabase::addTable(SqliteTable *newSqliteTable)
+{
+    newSqliteTable->setSqliteDatabase(this);
+    sqliteTables.append(newSqliteTable);
+}
+
+const QVector<SqliteTable *> &SqliteDatabase::tables() const
+{
+    return sqliteTables;
+}
+
+void SqliteDatabase::setDatabaseFilePath(const QString &databaseFilePath)
+{
+    databaseFilePath_ = databaseFilePath;
+}
+
+const QString &SqliteDatabase::databaseFilePath() const
+{
+    return databaseFilePath_;
+}
+
+void SqliteDatabase::setJournalMode(JournalMode journalMode)
+{
+    journalMode_ = journalMode;
+}
+
+JournalMode SqliteDatabase::journalMode() const
+{
+    return journalMode_;
+}
+
+QThread *SqliteDatabase::writeWorkerThread() const
+{
+    return writeDatabaseConnection.connectionThread();
+}
+
+QThread *SqliteDatabase::readWorkerThread() const
+{
+    return readDatabaseConnection.connectionThread();
+}
+
+void SqliteDatabase::handleReadDatabaseConnectionIsOpened()
+{
+    if (writeDatabaseConnection.isOpen() && readDatabaseConnection.isOpen()) {
+        initializeTables();
+        emit databaseIsOpened();
+    }
+}
+
+void SqliteDatabase::handleWriteDatabaseConnectionIsOpened()
+{
+    readDatabaseConnection.setDatabaseFilePath(databaseFilePath());
+}
+
+void SqliteDatabase::handleReadDatabaseConnectionIsClosed()
+{
+    if (!writeDatabaseConnection.isOpen() && !readDatabaseConnection.isOpen()) {
+        shutdownTables();
+        emit databaseIsClosed();
+    }
+}
+
+void SqliteDatabase::handleWriteDatabaseConnectionIsClosed()
+{
+    readDatabaseConnection.close();
+}
+
+void SqliteDatabase::initializeTables()
+{
+    for (SqliteTable *table: tables())
+        table->initialize();
+}
+
+void SqliteDatabase::shutdownTables()
+{
+    for (SqliteTable *table: tables())
+        table->shutdown();
+}
+
+