Fixes #1558. Support "thick divider" split view style in nib2cib.

The thick divider style is converted to the pane splitter style in nib2cib since we only use two styles in Cappuccino.

Tools/nib2cib/NSSplitView.j

@@ -22,6 +22,7 @@
 
 @import <AppKit/CPSplitView.j>
 
+var NSThinDividerStyle = 2;
 
 @implementation CPSplitView (CPCoding)
 
@@ -30,7 +31,11 @@
     if (self = [super NS_initWithCoder:aCoder])
     {
         _isVertical = [aCoder decodeBoolForKey:@"NSIsVertical"];
-        _isPaneSplitter = [aCoder decodeIntForKey:@"NSDividerStyle"] == 3;
+
+        // The possible values appear to be: no value (thick divider), 2 (thin divider) and 3 (pane splitter). For
+        // Cappuccino's purposes we treat thick divider and pane splitter as the same thing since the only difference
+        // seems to be graphical.
+        _isPaneSplitter = [aCoder decodeIntForKey:@"NSDividerStyle"] != NSThinDividerStyle;
 
         _autosaveName = [aCoder decodeObjectForKey:@"NSAutosaveName"];
     }