S390: Add new s390 platform z16.

The new IBM z16 is added to platform string array.
The macro _DL_PLATFORMS_COUNT is incremented.

_dl_hwcaps_subdir is extended by "z16" if HWCAP_S390_VXRS_PDE2
is set. HWCAP_S390_NNPA is not tested in _dl_hwcaps_subdirs_active
as those instructions may be replaced or removed in future.

tst-glibc-hwcaps.c is extended in order to test z16 via new marker5.

A fatal glibc error is dumped if glibc was build with architecture
level set for z16, but run on an older machine. (See dl-hwcap-check.h)