Patch drag & drop handler for old versions of macOS.

Currently this is a hack which simply disables most of the code.
This hack likely doesn't work.

--- ./src/interface/dropsource_mac.mm.orig	2022-06-01 15:56:30.000000000 +0200
+++ ./src/interface/dropsource_mac.mm	2023-03-25 20:24:32.000000000 +0100
@@ -7,6 +7,7 @@
 #include <wx/utils.h>
 #include <wx/filename.h>
 
+#include <AvailabilityMacros.h>
 #include <AppKit/AppKit.h>
 
 wxDragResult NSFileDragOperationToWxDragResult(NSDragOperation code)
@@ -30,6 +31,7 @@
 	return wxDragNone;
 }
 
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= 1070
 @interface FileDropSourceDelegate : NSObject<NSDraggingSource>
 {
 	BOOL dragFinished;
@@ -125,7 +127,9 @@
 }
 
 @end
+#endif
 
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= 101200
 @interface FilePromiseProviderDelegate : NSObject<NSFilePromiseProviderDelegate>
 {
 	NSOperationQueue * workQueue;
@@ -142,7 +146,9 @@
 {
 	self = [super init];
 	workQueue = [[NSOperationQueue alloc] init];
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= 101000
 	workQueue.qualityOfService = NSQualityOfServiceUserInitiated;
+#endif
 	path = nil;
 	return self;
 }
@@ -185,6 +191,7 @@
 	return workQueue;
 }
 @end
+#endif
 
 wxDragResult DropSource::DoFileDragDrop(int flags)
 {
@@ -200,8 +207,10 @@
 	NSEvent* theEvent = (NSEvent*)wxTheApp->MacGetCurrentEvent();
 	wxASSERT_MSG(theEvent, "DoDragDrop must be called in response to a mouse down or drag event.");
 
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= 1070
 	FileDropSourceDelegate* delegate = [[FileDropSourceDelegate alloc] init];
 	[delegate setImplementation:this flags:flags];
+#endif
 
 	// add a dummy square as dragged image for the moment,
 	// TODO: proper drag image for data
@@ -223,6 +232,7 @@
 
 	NSMutableArray *items = [[NSMutableArray alloc] init];
 
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= 101200
 	FilePromiseProviderDelegate * filePromiseDelegate = [[FilePromiseProviderDelegate alloc] init];
 	NSDraggingItem* draggingItem = [[NSDraggingItem alloc] initWithPasteboardWriter:[filePromiseDelegate pasteboardWriter]];
 	[draggingItem setDraggingFrame:NSMakeRect(p.x, p.y, 16, 16) contents:image];
@@ -248,6 +258,7 @@
 	[delegate release];
 	[image release];
 	[filePromiseDelegate release];
+#endif
 
 	wxWindow* mouseUpTarget = wxWindow::GetCapture();
 
@@ -261,6 +272,9 @@
 		wxevent.SetEventType(wxEVT_LEFT_UP);
 		mouseUpTarget->HandleWindowEvent(wxevent);
 	}
-
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= 101200
 	return result;
+#else
+	return wxDragError;
+#endif
 }