Generate an INST_PREDICATES table for each ISA.

Instead of generating a single `check_instp()` function, create an array
of individual function pointers for checking instruction predicates.

This makes explicit the jump table in the old check_instp() method and
it gives us a way of determining the number of instruction predicates
that exists.

lib/cretonne/src/isa/intel/mod.rs

@@ -74,8 +74,8 @@ impl TargetIsa for Isa {
                               Ok(Encodings::new(enclist_offset,
                                                 &enc_tables::ENCLISTS[..],
                                                 &enc_tables::RECIPE_PREDICATES[..],
+                                                &enc_tables::INST_PREDICATES[..],
                                                 inst,
-                                                enc_tables::check_instp,
                                                 self.isa_flags.predicate_view()))
                           })
     }