Move exp compat wrappers under math/

Move exp compat wrappers to math/w_exp{,f,l}_compat.c to be
consistent with other wrappers.

	* sysdeps/ieee754/dbl-64/w_exp_compat.c: Move to...
	* math/w_exp_compat.c: ... here.
	* sysdeps/ieee754/flt-32/w_expf_compat.c: Move to...
	* math/w_expf_compat.c: ... here.
	* sysdeps/ieee754/ldbl-128/w_expl_compat.c: Move to...
	* math/w_expl_compat.c: ... here.
	* sysdeps/ieee754/ldbl-128ibm/w_expl_compat.c: Remove.
	* sysdeps/ieee754/ldbl-96/w_expl_compat.c: Remove.
	* sysdeps/ieee754/ldbl-opt/w_exp_compat.c: Use the new path.
	* sysdeps/ieee754/ldbl-opt/w_expl_compat.c: Likewise.