Fix misc. clang warnings - mostly complaints about inconsistent use of override.

Previously, MacOpenFile only overrode anything on OS X; otherwise it was
just a useless method, which is presumably why it wasn't marked override
in the first place.  Address this more sanely by wrapping it in #ifdef
__APPLE__.

Source/Core/DolphinWX/ControllerConfigDiag.cpp

@@ -43,7 +43,7 @@ wxDEFINE_EVENT(wxEVT_ADAPTER_UPDATE, wxCommandEvent);
 ControllerConfigDiag::ControllerConfigDiag(wxWindow* const parent)
 	: wxDialog(parent, wxID_ANY, _("Dolphin Controller Configuration"))
 {
-	m_gc_pad_type_strs = {
+	m_gc_pad_type_strs = {{
 		_("None"),
 		_("Standard Controller"),
 		_("Steering Wheel"),
@@ -52,7 +52,7 @@ ControllerConfigDiag::ControllerConfigDiag(wxWindow* const parent)
 		_("GBA"),
 		_("Keyboard"),
 		_("AM-Baseboard")
-	};
+	}};
 
 	wxBoxSizer* const main_sizer = new wxBoxSizer(wxVERTICAL);
 

Source/Core/DolphinWX/Main.cpp

@@ -276,12 +276,14 @@ bool DolphinApp::OnInit()
 	return true;
 }
 
+#ifdef __APPLE__
 void DolphinApp::MacOpenFile(const wxString &fileName)
 {
 	FileToLoad = fileName;
 	LoadFile = true;
 	main_frame->BootGame(WxStrToStr(FileToLoad));
 }
+#endif
 
 void DolphinApp::AfterInit()
 {

Source/Core/DolphinWX/Main.h

@@ -23,7 +23,9 @@ private:
 	void OnFatalException() override;
 	bool Initialize(int& c, wxChar **v) override;
 	void InitLanguageSupport();
-	void MacOpenFile(const wxString &fileName);
+#ifdef __APPLE__
+	void MacOpenFile(const wxString &fileName) override;
+#endif
 
 	bool BatchMode;
 	bool LoadFile;

Source/Core/InputCommon/ControllerInterface/OSX/OSXKeyboard.h

@@ -57,9 +57,9 @@ public:
 
 	Keyboard(IOHIDDeviceRef device, std::string name, int index, void *window);
 
-	std::string GetName() const;
-	std::string GetSource() const;
-	int GetId() const;
+	std::string GetName() const override;
+	std::string GetSource() const override;
+	int GetId() const override;
 
 private:
 	struct