Qt5: Buildfix. Thanks to @Bigpet.

Implement an about section. Maybe this should run credits?
Fixes #4587

Qt/Settings.pri

@@ -13,6 +13,7 @@ INCLUDEPATH += ../ext/zlib ../native/ext/glew ../Common
 win32-msvc* {
 	QMAKE_CXXFLAGS_RELEASE += /O2 /arch:SSE2 /fp:fast
 	DEFINES += _MBCS GLEW_STATIC _CRT_SECURE_NO_WARNINGS
+	contains(DEFINES,UNICODE): DEFINES+=_UNICODE
 	PRECOMPILED_HEADER = ../Windows/stdafx.h
 	PRECOMPILED_SOURCE = ../Windows/stdafx.cpp
 	INCLUDEPATH += .. ../ffmpeg/Windows/$${QMAKE_TARGET.arch}/include

Qt/mainwindow.cpp

@@ -1,5 +1,13 @@
+// Qt Desktop UI: works on Linux, Windows and Mac OSX
 #include "mainwindow.h"
 
+#include <QApplication>
+#include <QDesktopServices>
+#include <QDesktopWidget>
+#include <QFileDialog>
+#include <QKeyEvent>
+#include <QMessageBox>
+
 #include "Core/MIPS/MIPSDebugInterface.h"
 #include "Core/Debugger/SymbolMap.h"
 #include "Core/SaveState.h"
@@ -12,8 +20,6 @@
 #include "QtHost.h"
 #include "qtemugl.h"
 
-// TODO: Make this class thread-aware. Can't send events to a different thread. Currently only works on X11.
-// Needs to use QueuedConnection for signals/slots.
 MainWindow::MainWindow(QWidget *parent) :
 	QMainWindow(parent),
 	nextState(CORE_POWERDOWN),
@@ -454,7 +460,7 @@ void MainWindow::websiteAct_triggered()
 
 void MainWindow::aboutAct_triggered()
 {
-	// TODO display about
+	QMessageBox::about(this, "PPSSPP Qt", QString::fromLocal8Bit("Created by Henrik Rydg\xc3\xa5rd"));
 }
 
 /* Private functions */

Qt/mainwindow.h

@@ -1,6 +1,11 @@
 #ifndef MAINWINDOW_H
 #define MAINWINDOW_H
 
+#include <QtCore>
+#include <QMenuBar>
+#include <QMainWindow>
+#include <QActionGroup>
+
 #include "ConsoleListener.h"
 #include "Core/Core.h"
 #include "Core/Config.h"
@@ -10,9 +15,6 @@
 #include "debugger_memorytex.h"
 #include "debugger_displaylist.h"
 
-#include <QtCore>
-#include <QtGui>
-
 class QtEmuGL;
 
 class MainWindow : public QMainWindow