Add an index_type field to Table.

This parallels the `index_type` field in `Heap`.

cranelift/filetests/verifier/table.clif

@@ -0,0 +1,46 @@
+test verifier
+target x86_64
+
+function %table_base_type(i64 vmctx) {
+    gv0 = vmctx+0
+    gv1 = deref(gv0): i32
+    table0 = dynamic gv1, element_size 1, bound gv1, index_type i32 ; error: table base has type i32, which is not the pointer type i64
+
+ebb0(v0: i64):
+    return
+}
+
+function %invalid_base(i64 vmctx) {
+    gv0 = vmctx+0
+    table0 = dynamic gv1, bound gv0, element_size 1, index_type i64 ; error: invalid base global value gv1
+
+ebb0(v0: i64):
+    return
+}
+
+function %invalid_bound(i64 vmctx) {
+    gv0 = vmctx+0
+    table0 = dynamic gv0, bound gv1, element_size 1, index_type i64 ; error: invalid bound global value gv1
+
+ebb0(v0: i64):
+    return
+}
+
+function %table_bound_type(i64 vmctx) {
+    gv0 = vmctx+0
+    gv1 = deref(gv0): i16
+    table0 = dynamic gv0, bound gv1, element_size 1, index_type i32 ; error: table index type i32 differs from the type of its bound, i16
+
+ebb0(v0: i64):
+    return
+}
+
+function %table_addr_index_type(i64 vmctx, i64) {
+    gv0 = vmctx+0
+    gv1 = deref(gv0): i32
+    table0 = dynamic gv0, element_size 1, bound gv1, index_type i32
+
+ebb0(v0: i64, v1: i64):
+    v2 = table_addr.i64 table0, v1, +0; error: index type i64 differs from table index type i32
+    return
+}