add Modifier for FunctionRegistry.

Author: lianhuiwang

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/FunctionRegistry.scala

@@ -17,6 +17,8 @@
 
 package org.apache.spark.sql.catalyst.analysis
 
+import java.lang.reflect.Modifier
+
 import scala.language.existentials
 import scala.reflect.ClassTag
 import scala.util.{Failure, Success, Try}