Fix macOS client/server failing to start from terminal

The macOS client and server were completely unusable when run from a
terminal. They blocked forever in `[NSApp run];` which was called by
Sys_InitProtocolHandler(). `applicationDidFinishLaunching` was never
called to exit the NSApp run loop.

Use SDL's SDL_DROPFILE event to receive URLs to handle on macOS instead.
This also handles URLs while the game is running (connect to new server)
instead of nothing happening when clicking a link while the game is
running.

code/sys/sys_osx.m

@@ -34,10 +34,6 @@ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 #import <Carbon/Carbon.h>
 #import <Cocoa/Cocoa.h>
 
-#ifdef PROTOCOL_HANDLER
-char *protocolCommand = NULL;
-#endif
-
 /*
 ==============
 Sys_Dialog
@@ -119,42 +115,3 @@ char *Sys_StripAppBundle( char *dir )
 	Q_strncpyz(cwd, Sys_Dirname(cwd), sizeof(cwd));
 	return cwd;
 }
-
-#ifdef PROTOCOL_HANDLER
-
-@interface AppDelegate : NSObject <NSApplicationDelegate>
-@end
-
-@implementation AppDelegate
-
-- (void)handleAppleEvent:(NSAppleEventDescriptor *)event withReplyEvent: (NSAppleEventDescriptor *)replyEvent
-{
-	NSString *input = [[event paramDescriptorForKeyword:keyDirectObject] stringValue];
-	protocolCommand = Sys_ParseProtocolUri( input.UTF8String );
-}
-
-- (void)applicationDidFinishLaunching:(NSNotification *)notification
-{
-	[NSApp stop:nil];
-}
-
-@end
-
-char *Sys_InitProtocolHandler( void )
-{
-	[NSApplication sharedApplication];
-
-	AppDelegate *appDelegate = [AppDelegate new];
-	NSAppleEventManager *sharedAppleEventManager = [NSAppleEventManager new];
-	[sharedAppleEventManager setEventHandler:appDelegate
-	                             andSelector:@selector(handleAppleEvent:withReplyEvent:)
-	                           forEventClass:kInternetEventClass
-	                              andEventID:kAEGetURL];
-
-	[NSApp setDelegate:appDelegate];
-	[NSApp run];
-
-	return protocolCommand;
-}
-
-#endif