ecpg: Change --version output to common style

When we removed the ecpg-specific versions, we also removed the
"(PostgreSQL)" from the --version output, which we show in other
programs.
Reported-by: Ioseph Kim <pgsql-kr@postgresql.kr>

src/interfaces/ecpg/preproc/ecpg.c

@@ -149,7 +149,7 @@ main(int argc, char *const argv[])
 		}
 		if (strcmp(argv[1], "--version") == 0 || strcmp(argv[1], "-V") == 0)
 		{
-			printf("ecpg %s\n", PG_VERSION);
+			printf("ecpg (PostgreSQL) %s\n", PG_VERSION);
 			exit(0);
 		}
 	}