Remove bogus "extern" annotations on function definitions.

While this is not illegal C, project style is to put "extern" only on
declarations not definitions.

David Rowley

Discussion: https://postgr.es/m/CAKJS1f9RKLWXcMBQhvDYhmsMEo+ALuNgA-NE+AX5Uoke9DJ2Xg@mail.gmail.com

contrib/postgres_fdw/deparse.c

@@ -927,7 +927,7 @@ build_tlist_to_deparse(RelOptInfo *foreignrel)
  *
  * List of columns selected is returned in retrieved_attrs.
  */
-extern void
+void
 deparseSelectStmtForRel(StringInfo buf, PlannerInfo *root, RelOptInfo *rel,
 						List *tlist, List *remote_conds, List *pathkeys,
 						bool is_subquery, List **retrieved_attrs,
@@ -1313,7 +1313,7 @@ appendConditions(List *exprs, deparse_expr_cxt *context)
 }
 
 /* Output join name for given join type */
-extern const char *
+const char *
 get_jointype_name(JoinType jointype)
 {
 	switch (jointype)

contrib/postgres_fdw/postgres_fdw.c

@@ -5567,7 +5567,7 @@ conversion_error_callback(void *arg)
  * Find an equivalence class member expression, all of whose Vars, come from
  * the indicated relation.
  */
-extern Expr *
+Expr *
 find_em_expr_for_rel(EquivalenceClass *ec, RelOptInfo *rel)
 {
 	ListCell   *lc_em;