SEC-974: Made getExceptionMappings() protected.

core/src/main/java/org/springframework/security/ui/AbstractProcessingFilter.java

@@ -482,7 +482,7 @@ public abstract class AbstractProcessingFilter extends SpringSecurityFilter impl
         this.defaultTargetUrl = defaultTargetUrl;
     }
 
-    Properties getExceptionMappings() {
+    protected Properties getExceptionMappings() {
         return new Properties(exceptionMappings);
     }