Add a trapff instruction.

This is the floating point equivalent of trapif: Trap when a given
condition is in the floating-point flags.

Define Intel encodings comparable to the trapif encodings.

lib/cretonne/src/verifier/mod.rs

@@ -366,6 +366,7 @@ impl<'a> Verifier<'a> {
             Trap { .. } |
             CondTrap { .. } |
             IntCondTrap { .. } |
+            FloatCondTrap { .. } |
             NullAry { .. } => {}
         }