Use generic alias macros in ldbl-opt.

Use generic alias macros in ldbl-opt.

This patch fixes ldbl-opt code to use generic libm alias macros in
preparation for getting _FloatN / _FloatNx aliases where appropriate.

Four functions are affected, that undefine and redefine alias macros
before including the implementations they wrap in such a way that
_FloatN / _FloatNx aliases would not appear.  s_clog10l.c undefines
and redefined declare_mgen_alias, so just needs a
libm_alias_ldouble_other call added.  w_exp10l_compat.c undefines and
redefines weak_alias, but in fact does not need to do so, since
math/w_exp10l_compat.c uses libm_alias_ldouble and does not use
weak_alias other than through that, so the undefines and redefines of
weak_alias are removed.  w_lgamma_compatl.c and w_remainderl_compat.c
are made to use libm_alias_ldouble_other in conjunction with restoring
the original definition of weak_alias so this is effective.

Tested with build-many-glibcs.py.  Installed stripped shared libraries
are unchanged by this patch.

	* sysdeps/ieee754/ldbl-opt/s_clog10l.c: Use
	libm_alias_ldouble_other.
	* sysdeps/ieee754/ldbl-opt/w_exp10l_compat.c (weak_alias): Do not
	undefine and redefine.
	[LIBM_SVID_COMPAT && !LONG_DOUBLE_COMPAT (libm, GLIBC_2_1)]
	(exp10l): Do not define here.
	* sysdeps/ieee754/ldbl-opt/w_lgamma_compatl.c [BUILD_LGAMMA]
	(weak_alias): Undefine and redefine.
	[BUILD_LGAMMA]: Use libm_alias_ldouble_other.
	* sysdeps/ieee754/ldbl-opt/w_remainderl_compat.c
	[LIBM_SVID_COMPAT] (weak_alias): Undefine and redefine here.
	[LIBM_SVID_COMPAT]: Use libm_alias_ldouble_other.