Correct some ia64 libm_alias_float_other calls.

Correct some ia64 libm_alias_float_other calls.

This patch corrects three ia64 libm_alias_float_other calls so they
generate the intended _Float32 aliases when such aliases are enabled.

Tested with build-many-glibcs.py for ia64-linux-gnu (that installed
stripped shared libraries are unchanged when applied to current
sources, and that this enables compilation tests to pass when used in
conjunction with other _Float32 patches).

	* sysdeps/ia64/fpu/e_exp2f.S (__exp2f): Use exp2 not __exp2 as
	second argument to libm_alias_float_other.
	* sysdeps/ia64/fpu/e_log2f.S (__log2f): Use log2 not __log2 as
	second argument to libm_alias_float_other.
	* sysdeps/ia64/fpu/e_powf.S (__powf): Use pow not __pow as second
	argument to libm_alias_float_other.