IPCCompiler+WindowServer: Fix deleted function warning

It might be the case that we are passing non-movable/non-copyable things
through IPC. In this case, Clang will emit a warning as it can't
generate the requested default move/copy ctor for the IPC message.

To fix this, we use a `#pragma` to make the compiler silently ignore our
request.

The same was the case with the three-way comparison in `Screen`. Since
we don't use the three-way comparison operator anywhere else in our
codebase, we simply use the `==` operator instead.

Userland/DevTools/IPCCompiler/main.cpp

@@ -284,6 +284,11 @@ int main(int argc, char** argv)
 #include <LibIPC/File.h>
 #include <LibIPC/Message.h>
 #include <LibIPC/Stub.h>
+
+#ifdef __clang__
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdefaulted-function-deleted"
+#endif
 )~~~");
 
     for (auto& endpoint : endpoints) {
@@ -865,6 +870,10 @@ public:
         endpoint_generator.append(R"~~~(
 private:
 };
+
+#ifdef __clang__
+#pragma clang diagnostic pop
+#endif
 )~~~");
     }