Fix C++ incompatibilities in plpgsql's header files.

Rename some exposed parameters so that they don't conflict with
C++ reserved words.

Back-patch to all supported versions.

George Tarasov

Discussion: https://postgr.es/m/b517ec3918d645eb950505eac8dd434e@gaz-is.ru

src/pl/plpgsql/src/plpgsql.h

@@ -941,7 +941,7 @@ extern PLpgSQL_rec *plpgsql_build_record(const char *refname, int lineno,
 extern int plpgsql_recognize_err_condition(const char *condname,
 								bool allow_sqlstate);
 extern PLpgSQL_condition *plpgsql_parse_err_condition(char *condname);
-extern void plpgsql_adddatum(PLpgSQL_datum *new);
+extern void plpgsql_adddatum(PLpgSQL_datum *newdatum);
 extern int	plpgsql_add_initdatums(int **varnos);
 extern void plpgsql_HashTableInit(void);
 
@@ -969,7 +969,7 @@ extern Oid exec_get_datum_type(PLpgSQL_execstate *estate,
 					PLpgSQL_datum *datum);
 extern void exec_get_datum_type_info(PLpgSQL_execstate *estate,
 						 PLpgSQL_datum *datum,
-						 Oid *typeid, int32 *typmod, Oid *collation);
+						 Oid *typeId, int32 *typMod, Oid *collation);
 
 /* ----------
  * Functions for namespace handling in pl_funcs.c