Use libm_alias_double for coldfire.

Continuing the preparation for additional _FloatN / _FloatNx function
aliases, this patch makes coldfire libm function implementations use
libm_alias_double to define function aliases.

Untested, given the currently broken state of GCC for coldfire.

	* sysdeps/m68k/coldfire/fpu/s_fabs.c: Include
	<libm-alias-double.h>.
	(fabs): Define using libm_alias_double.
	* sysdeps/m68k/coldfire/fpu/s_lrint.c: Include
	<libm-alias-double.h>.
	(lrint): Define using libm_alias_double.
	* sysdeps/m68k/coldfire/fpu/s_rint.c: Include
	<libm-alias-double.h>.
	(rint): Define using libm_alias_double.