Update copyrights for 2020

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

src/backend/optimizer/util/appendinfo.c

@@ -3,7 +3,7 @@
  * appendinfo.c
  *	  Routines for mapping between append parent(s) and children
  *
- * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  *

src/backend/optimizer/util/clauses.c

@@ -3,7 +3,7 @@
  * clauses.c
  *	  routines to manipulate qualification clauses
  *
- * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  *

src/backend/optimizer/util/inherit.c

@@ -3,7 +3,7 @@
  * inherit.c
  *	  Routines to process child relations in inheritance trees
  *
- * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  *

src/backend/optimizer/util/joininfo.c

@@ -3,7 +3,7 @@
  * joininfo.c
  *	  joininfo list manipulation routines
  *
- * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  *

src/backend/optimizer/util/orclauses.c

@@ -3,7 +3,7 @@
  * orclauses.c
  *	  Routines to extract restriction OR clauses from join OR clauses
  *
- * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  *

src/backend/optimizer/util/paramassign.c

@@ -40,7 +40,7 @@
  * doesn't really save much executor work anyway.
  *
  *
- * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION

src/backend/optimizer/util/pathnode.c

@@ -3,7 +3,7 @@
  * pathnode.c
  *	  Routines to manipulate pathlists and create path nodes
  *
- * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  *

src/backend/optimizer/util/placeholder.c

@@ -4,7 +4,7 @@
  *	  PlaceHolderVar and PlaceHolderInfo manipulation routines
  *
  *
- * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  *

src/backend/optimizer/util/plancat.c

@@ -4,7 +4,7 @@
  *	   routines for accessing the system catalogs
  *
  *
- * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  *

src/backend/optimizer/util/predtest.c

@@ -4,7 +4,7 @@
  *	  Routines to attempt to prove logical implications between predicate
  *	  expressions.
  *
- * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  *

src/backend/optimizer/util/relnode.c

@@ -3,7 +3,7 @@
  * relnode.c
  *	  Relation-node lookup/construction routines
  *
- * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  *

src/backend/optimizer/util/restrictinfo.c

@@ -3,7 +3,7 @@
  * restrictinfo.c
  *	  RestrictInfo node manipulation routines.
  *
- * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  *

src/backend/optimizer/util/tlist.c

@@ -3,7 +3,7 @@
  * tlist.c
  *	  Target list manipulation routines
  *
- * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  *

src/backend/optimizer/util/var.c

@@ -9,7 +9,7 @@
  * contains variables.
  *
  *
- * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  *