smdb_add_extension
extern int smdb_add_extension __P((char *, int, char *, char *));
result = smdb_add_extension(file_name, sizeof file_name, db_name,
result = smdb_add_extension(db_file_name, sizeof db_file_name, db_name,
result = smdb_add_extension(db_file_name, sizeof db_file_name, db_name,
result = smdb_add_extension(db_file_name, sizeof db_file_name,
result = smdb_add_extension(db_file_name, sizeof db_file_name,