[PATCH] Use TEST_COMPARE_STRING in recently added test

[Florian Weimer]

* Gabriel F. T. Gomes:

> 	* argp/tst-ldbl-argp.c (do_one_test): Use TEST_COMPARE_STRING,
> 	instead of manually comparing and reporting mismatching strings.
> 	* misc/tst-ldbl-error.c (do_one_test): Likewise.
> 	* misc/tst-ldbl-warn.c (do_one_test): Likewise.

Patch looks okay to me.  Thanks.

Florian