New QGCFileDialog apis

Using QFileDialog directly on OS X can hang intermittently due to Qt
bug. QGCFileDialog works around this by not using the native dialogs.

src/QGCFileDialog.h

+/*=====================================================================
+ 
+ QGroundControl Open Source Ground Control Station
+ 
+ (c) 2009 - 2014 QGROUNDCONTROL PROJECT <http://www.qgroundcontrol.org>
+ 
+ This file is part of the QGROUNDCONTROL project
+ 
+ QGROUNDCONTROL is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+ 
+ QGROUNDCONTROL is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ GNU General Public License for more details.
+ 
+ You should have received a copy of the GNU General Public License
+ along with QGROUNDCONTROL. If not, see <http://www.gnu.org/licenses/>.
+ 
+ ======================================================================*/
+
+#ifndef QGCFILEDIALOG_H
+#define QGCFILEDIALOG_H
+
+#include <QFileDialog>
+
+/// @file
+///     @brief Subclass of QFileDialog which re-implements the static public functions. The reason for this
+///             is that the QFileDialog implementations of these use the native os dialogs. On OSX these
+///             these can intermittently hang. So instead here we use the native dialogs.
+///     @author Don Gagne <don@thegagnes.com>
+
+class QGCFileDialog : public QFileDialog {
+    
+public:
+    static QString getExistingDirectory(QWidget* parent = 0, const QString& caption = QString(), const QString& dir = QString(), Options options = ShowDirsOnly)
+        { return QFileDialog::getExistingDirectory(parent, caption, dir, options | DontUseNativeDialog); }
+    
+    static QString getOpenFileName(QWidget* parent = 0, const QString& caption = QString(), const QString& dir = QString(), const QString& filter = QString(), QString* selectedFilter = 0, Options options = 0)
+        { return QFileDialog::getOpenFileName(parent, caption, dir, filter, selectedFilter, options | DontUseNativeDialog); }
+    
+    static QStringList getOpenFileNames(QWidget* parent = 0, const QString& caption = QString(), const QString& dir = QString(), const QString& filter = QString(), QString* selectedFilter = 0, Options options = 0)
+        { return QFileDialog::getOpenFileNames(parent, caption, dir, filter, selectedFilter, options | DontUseNativeDialog); }
+    
+    static QString getSaveFileName(QWidget* parent = 0, const QString& caption = QString(), const QString& dir = QString(), const QString& filter = QString(), QString* selectedFilter = 0, Options options = 0)
+        { return QFileDialog::getSaveFileName(parent, caption, dir, filter, selectedFilter, options | DontUseNativeDialog); }
+};
+
+
+#endif