sim/common: wire up new unordered comparisons

Define and wire up unordered floating point comparison operations for cgen
targets.  This patch depends on my posted cgen patches[0].

[0] https://www.sourceware.org/ml/cgen/2019-q2/msg00013.html

sim/common/ChangeLog:

yyyy-mm-dd  Stafford Horne  <shorne@gmail.com>

	* cgen-accfp.c (unorderedsf, unordereddf): New functions.
	(cgen_init_accurate_fpu): Wire up unorderedsf and unordereddf.
	* cgen-fpu.h (cgen_fp_ops): Define fields unorderedsf and unordereddf.