Update copyrights for 2020

Backpatch-through: update all files in master, backpatch legal files through 9.4

Author: bmomjian

COPYRIGHT

@@ -1,7 +1,7 @@
 PostgreSQL Database Management System
 (formerly known as Postgres, then as Postgres95)
 
-Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
+Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
 
 Portions Copyright (c) 1994, The Regents of the University of California
 

configure

@@ -11,7 +11,7 @@
 # This configure script is free software; the Free Software Foundation
 # gives unlimited permission to copy, distribute and modify it.
 #
-# Copyright (c) 1996-2019, PostgreSQL Global Development Group
+# Copyright (c) 1996-2020, PostgreSQL Global Development Group
 ## -------------------- ##
 ## M4sh Initialization. ##
 ## -------------------- ##
@@ -1669,7 +1669,7 @@ Copyright (C) 2012 Free Software Foundation, Inc.
 This configure script is free software; the Free Software Foundation
 gives unlimited permission to copy, distribute and modify it.
 
-Copyright (c) 1996-2019, PostgreSQL Global Development Group
+Copyright (c) 1996-2020, PostgreSQL Global Development Group
 _ACEOF
   exit
 fi