sim: Add partial support for IEEE 754-2008

2022-02-01  Faraz Shahbazker  <fshahbazker@wavecomp.com>

sim/common/ChangeLog:
	* sim-fpu.c (sim_fpu_minmax_nan): New.
	(sim_fpu_max): Add variant behaviour for IEEE 754-2008.
	(sim_fpu_min): Likewise.
	(sim_fpu_is_un, sim_fpu_is_or): New.
	(sim_fpu_un, sim_fpu_or): New.
	(sim_fpu_is_ieee754_2008, sim_fpu_is_ieee754_1985): New.
	(sim_fpu_set_mode): New.
	(sim_fpu_classify): New.
	* sim-fpu.h (sim_fpu_minmax_nan): New declaration.
	(sim_fpu_un, sim_fpu_or): New declarations.
	(sim_fpu_is_un, sim_fpu_is_or): New declarations.
	(sim_fpu_mode): New enum.
	[sim_fpu_state](current_mode): New field.
	(sim_fpu_current_mode): New define.
	(sim_fpu_is_ieee754_2008): New declaration.
	(sim_fpu_is_ieee754_1985): New declaration.
	(sim_fpu_set_mode): New declaration.
	(sim_fpu_classify): New declaration.