Obsolete p_secstodate

[Florian Weimer]

* Joseph Myers:

> 2017-11-22  Joseph Myers  <joseph@codesourcery.com>
>
> 	* resolv/res_debug.c (p_secstodate): Condition definition on
> 	[SHLIB_COMPAT (libresolv, GLIBC_2_0, GLIBC_2_27)].  Define
> 	directly as __p_secstodate, and as a compat symbol.  Do not use
> 	libresolv_hidden_def.
> 	* resolv/resolv.h (p_secstodate): Remove macro and function
> 	declaration.
> 	* resolv/ns_print.c (ns_sprintrrf): Print times with %lu, not
> 	using p_secstodate.
> 	* include/resolv.h (__p_secstodate): Do not use
> 	libresolv_hidden_proto.
> 	* resolv/Makefile (tests): Move tst-p_secstodate to ....
> 	(tests-internal): ... here.
> 	* resolv/tst-p_secstodate.c: Include <shlib-compat.h>.  Condition
> 	all contents on [TEST_COMPAT (libresolv, GLIBC_2_0, GLIBC_2_27)]
> 	and declare and use __p_secstodate and use compat_symbol_reference
> 	in that case.
> 	[!TEST_COMPAT (libresolv, GLIBC_2_0, GLIBC_2_27)] (do_test): Add
> 	implementation returning 77.

Looks good to me too.