Remove unused #include's from backend .c files

as determined by include-what-you-use (IWYU)

While IWYU also suggests to *add* a bunch of #include's (which is its
main purpose), this patch does not do that.  In some cases, a more
specific #include replaces another less specific one.

Some manual adjustments of the automatic result:

- IWYU currently doesn't know about includes that provide global
  variable declarations (like -Wmissing-variable-declarations), so
  those includes are being kept manually.

- All includes for port(ability) headers are being kept for now, to
  play it safe.

- No changes of catalog/pg_foo.h to catalog/pg_foo_d.h, to keep the
  patch from exploding in size.

Note that this patch touches just *.c files, so nothing declared in
header files changes in hidden ways.

As a small example, in src/backend/access/transam/rmgr.c, some IWYU
pragma annotations are added to handle a special case there.

Discussion: https://www.postgresql.org/message-id/flat/af837490-6b2f-46df-ba05-37ea6a6653fc%40eisentraut.org

src/backend/parser/analyze.c

@@ -48,10 +48,8 @@
 #include "parser/parse_target.h"
 #include "parser/parse_type.h"
 #include "parser/parsetree.h"
-#include "rewrite/rewriteManip.h"
 #include "utils/backend_status.h"
 #include "utils/builtins.h"
-#include "utils/guc.h"
 #include "utils/rel.h"
 #include "utils/syscache.h"
 

src/backend/parser/parse_clause.c

@@ -20,10 +20,8 @@
 #include "access/table.h"
 #include "access/tsmapi.h"
 #include "catalog/catalog.h"
-#include "catalog/heap.h"
 #include "catalog/pg_am.h"
 #include "catalog/pg_amproc.h"
-#include "catalog/pg_collation.h"
 #include "catalog/pg_constraint.h"
 #include "catalog/pg_type.h"
 #include "commands/defrem.h"

src/backend/parser/parse_merge.c

@@ -16,12 +16,10 @@
 #include "postgres.h"
 
 #include "access/sysattr.h"
-#include "miscadmin.h"
 #include "nodes/makefuncs.h"
 #include "parser/analyze.h"
 #include "parser/parse_collate.h"
 #include "parser/parsetree.h"
-#include "parser/parser.h"
 #include "parser/parse_clause.h"
 #include "parser/parse_cte.h"
 #include "parser/parse_expr.h"
@@ -29,7 +27,6 @@
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
 #include "utils/rel.h"
-#include "utils/relcache.h"
 
 static void setNamespaceForMergeWhen(ParseState *pstate,
 									 MergeWhenClause *mergeWhenClause,

src/backend/parser/parse_node.c

@@ -22,14 +22,9 @@
 #include "nodes/miscnodes.h"
 #include "nodes/nodeFuncs.h"
 #include "nodes/subscripting.h"
-#include "parser/parse_coerce.h"
-#include "parser/parse_expr.h"
-#include "parser/parse_relation.h"
-#include "parser/parsetree.h"
+#include "parser/parse_node.h"
 #include "utils/builtins.h"
 #include "utils/lsyscache.h"
-#include "utils/syscache.h"
-#include "utils/varbit.h"
 
 static void pcb_error_callback(void *arg);
 

src/backend/parser/parse_target.c

@@ -14,6 +14,7 @@
  */
 #include "postgres.h"
 
+#include "catalog/namespace.h"
 #include "catalog/pg_type.h"
 #include "commands/dbcommands.h"
 #include "funcapi.h"
@@ -22,7 +23,6 @@
 #include "nodes/nodeFuncs.h"
 #include "parser/parse_coerce.h"
 #include "parser/parse_expr.h"
-#include "parser/parse_func.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
 #include "parser/parse_type.h"
@@ -30,7 +30,6 @@
 #include "utils/builtins.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
-#include "utils/typcache.h"
 
 static void markTargetListOrigin(ParseState *pstate, TargetEntry *tle,
 								 Var *var, int levelsup);