Bug 237067 Solaris (forte) build is broken since nsTablePainter.h landing

r/sr/a=dbaron
Fix the bustage on Solaris.

layout/html/table/src/nsTablePainter.h

@@ -237,6 +237,8 @@ class TableBackgroundPainter
       nsStyleBorder* mSynthBorder;
     };
 
+    struct ColData;
+    friend struct ColData;
     struct ColData {
       TableBackgroundData  mCol;
       TableBackgroundData* mColGroup; //link to col's parent colgroup's data (owned by painter)

layout/tables/nsTablePainter.h

@@ -237,6 +237,8 @@ class TableBackgroundPainter
       nsStyleBorder* mSynthBorder;
     };
 
+    struct ColData;
+    friend struct ColData;
     struct ColData {
       TableBackgroundData  mCol;
       TableBackgroundData* mColGroup; //link to col's parent colgroup's data (owned by painter)