Check for invalid special type constraints.

The extend and reduce instructions have additional type constraints.

Stop inserting sextend instructions after ctz, clz, and popcnt when
translating from WebAssembly. The Cretonne instructions have the same
signature as the WebAssembly equivalents.

cranelift/filetests/verifier/type_check.cton

@@ -95,3 +95,17 @@ function %jump_args2() {
     ebb1(v10: i64, v11: i16):
         return
 }
+
+function %bad_extend() {
+ebb0:
+    v0 = iconst.i32 10
+    v1 = uextend.i16 v0 ; error: input i32 must be smaller than output i16
+    return
+}
+
+function %bad_reduce() {
+ebb0:
+    v0 = iconst.i32 10
+    v1 = ireduce.i64 v0 ; error: input i32 must be larger than output i64
+    return
+}