DolphinQt/Settings: Replace includes with forward declarations

Avoids dragging in netplay-related headers where they aren't explicitly
necessary.

Source/Core/DolphinQt/NetPlay/MD5Dialog.cpp

@@ -13,6 +13,9 @@
 #include <QProgressBar>
 #include <QVBoxLayout>
 
+#include "Core/NetPlayClient.h"
+#include "Core/NetPlayServer.h"
+
 #include "DolphinQt/Settings.h"
 
 static QString GetPlayerNameFromPID(int pid)

Source/Core/DolphinQt/NetPlay/PadMappingDialog.cpp

@@ -3,15 +3,17 @@
 // Refer to the license.txt file included.
 
 #include "DolphinQt/NetPlay/PadMappingDialog.h"
-#include "DolphinQt/Settings.h"
-
-#include "Core/NetPlayClient.h"
 
 #include <QComboBox>
 #include <QDialogButtonBox>
 #include <QGridLayout>
 #include <QLabel>
 
+#include "Core/NetPlayClient.h"
+#include "Core/NetPlayServer.h"
+
+#include "DolphinQt/Settings.h"
+
 PadMappingDialog::PadMappingDialog(QWidget* parent) : QDialog(parent)
 {
   setWindowFlags(windowFlags() & ~Qt::WindowContextHelpButtonHint);