Do not wrap logf, log2f and powf

The new generic logf, log2f and powf code don't need wrappers any more,
they set errno inline so only use the wrappers on targets that need it.

	* sysdeps/ieee754/flt-32/e_log2f.c (__log2f): Define without wrapper.
	* sysdeps/ieee754/flt-32/e_logf.c (__logf): Likewise
	* sysdeps/ieee754/flt-32/e_powf.c (__powf): Likewise
	* sysdeps/ieee754/flt-32/w_log2f.c: New file.
	* sysdeps/ieee754/flt-32/w_logf.c: New file.
	* sysdeps/ieee754/flt-32/w_powf.c: New file.
	* sysdeps/i386/fpu/w_log2f.c: New file.
	* sysdeps/i386/fpu/w_logf.c: New file.
	* sysdeps/i386/fpu/w_powf.c: New file.
	* sysdeps/m68k/m680x0/fpu/w_log2f.c: New file.
	* sysdeps/m68k/m680x0/fpu/w_logf.c: New file.
	* sysdeps/m68k/m680x0/fpu/w_powf.c: New file.