Settings: Performance optimizations

The syncing methods of sqlite are tremendously slow on
Linux and Windows at least.

Change-Id: I191e402db9aecdc153f5904e9bc9128c08fb9de4
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
Reviewed-by: hjk <hjk121@nokiamail.com>

src/plugins/coreplugin/settingsdatabase.cpp

@@ -131,6 +131,9 @@ SettingsDatabase::SettingsDatabase(const QString &path,
                 d->m_settings.insert(query.value(0).toString(), QVariant());
             }
         }
+
+        // syncing can be slow, especially on Linux and Windows
+        d->m_db.exec(QLatin1String("PRAGMA synchronous = OFF;"));
     }
 }