Catch NaN explicitly in expand_fcvt_to_uint().
Catch NaN explicitly in expand_fcvt_to_uint().

When the input is a NaN, we need to generate a different trap code, so
use the new trapff instruction to generate such a trap after the first
floating point comparison.

sunfishcode/cretonne,stoklund/cretonne,sunfishcode/cretonne,stoklund/cretonne,sunfishcode/cretonne,stoklund/cretonne