Work around unwanted MacOpenFiles() calls in wxOSX applications

Don't try to open any command line arguments as files by using the workaround
from Colin Barrett (see https://bugzilla.mozilla.org/show_bug.cgi?id=366009).

docs/changes.txt

@@ -128,6 +128,7 @@ wxOSX:
 - Implement wxDataViewChoiceByIndexRenderer (wanup).
 - Fix unnecessary indentation in list-like wxDataViewCtrl (Andreas Falkenhahn).
 - Recognize macOS 10.12 Sierra in wxGetOsDescription() (Tobias Taschner).
+- Don't try to open command line arguments as files (Jeff Hostetler).
 
 Unix:
 

src/osx/cocoa/utils.mm

@@ -421,6 +421,11 @@ bool wxApp::DoInitGui()
     }
     gNSLayoutManager = [[NSLayoutManager alloc] init];
     
+    // This call makes it so that appplication:openFile: doesn't get bogus calls
+    // from Cocoa doing its own parsing of the argument string. And yes, we need
+    // to use a string with a boolean value in it. That's just how it works.
+    [[NSUserDefaults standardUserDefaults] setObject:@"NO" forKey:@"NSTreatUnknownArgumentsAsOpen"];
+
     return true;
 }