ldbl-128ibm-compat: Add wide character printing functions

Similarly to what was done for regular character printing functions,
this patch uses the new mode mask, PRINTF_LDBL_USES_FLOAT128, in the
'mode' argument of the wide characters printing function,
__vfwprintf_internal (which is also extended to support printing
floating-point values with IEEE binary128, by saving floating-point
values into variables of type __float128 and adjusting the parameters to
__printf_fp and __printf_fphex as if it was a call from a wide-character
version of strfromf128 (even though such version does not exist)).

Tested for powerpc64le.

Reviewed-By: Paul E. Murphy <murphyp@linux.ibm.com>