Add operator== and != for some structs.

operator== and != are defined for type T where T is
one of the following:
* scalars
* strings
* enums
* U[] where U is in this list
* vec<U> where U is in this list
* structs that contain only types in this list.

If a struct contains a handle, an MQDescriptor,
or a union, for example, then == and != is not generated.

Bug: 32834072

Test: hidl_test
Change-Id: Icac73a14f81274ee6592e2b8fadf26d629151d9f
diff --git a/ArrayType.h b/ArrayType.h
index a7e5083..e17df10 100644
--- a/ArrayType.h
+++ b/ArrayType.h
@@ -33,6 +33,7 @@
     ArrayType(Type *elementType, ConstantExpression *size);
 
     bool isArray() const override;
+    bool canCheckEquality() const override;
 
     Type *getElementType() const;