Detect presence of NSCellUndoManager

Author: qmfrederik

Source/NSCell.m

@@ -75,6 +75,12 @@
 #import "GSGuiPrivate.h"
 #import "AppKit/NSTextFieldCell.h"
 #import "AppKit/NSSearchFieldCell.h"
+
+// Use NSAppleEventDescriptor as a proxy for detecting the Eggplant fork of libs-base
+#if !__has_include("Foundation/NSAppleEventDescriptor.h")
+#define HAVE_NSCellUndoManager
+#endif
+
 static Class colorClass;
 static Class cellClass;
 static Class fontClass;
@@ -2356,6 +2362,7 @@ incorrectly be reduced to zero (since the text object has no contents at
   _cell.in_editing = YES;
 
   // TESTPLANT-MAL-12282916: Paul Landers added this code...need to keep it...
+#ifdef HAVE_NSCellUndoManager
   if ([textObject isKindOfClass:[NSTextView class]])
     {
 	  NSCellUndoManager * undoManager = [[NSCellUndoManager alloc] init];
@@ -2364,7 +2371,7 @@ incorrectly be reduced to zero (since the text object has no contents at
 	  [undoManager release];
 	  [(NSTextView *)textObject setAllowsUndo:YES];
     }
-
+#endif
 
 #if 1
   // Testplant-MAL-2015-06-20: merging removal causes focus ring issues...