Add note :NO-FLOATING-POINT-UNDERFLOW-BY-DEFAULT
This note assumes that the implementation purposefully does not conform to 12.1.4.3 by not signaling FLOATING-POINT-UNDERFLOW by default. (The implementation should have an option of toggling this behaviour off in order to be able to signal this condition when underflows occur.)
Tests EXP{T,}.{8,9,10,11} have been annotated with this note.