This provides a extra macro expansion before invoking
the hidden_def macro. This is necessary to build the
ldbl-128 files as float128 correctly.
* sysdeps/generic/math_private.h:
(mathx_hidden_def): New macro.
* sysdeps/ieee754/ldbl-128/s_finitel.c: Replace hidden_def with
the above.
* sysdeps/ieee754/ldbl-128/s_isinfl.c: Likewise.
* sysdeps/ieee754/ldbl-128/s_isnanl.c: Likewise.