Reimplement CheckClass and IsPointerEqual functions

- The definition of FxGlobalFunctionCall_CheckClass was big and scary. I
  would say this is a big improvement, since now it gets to leverage the
  same framework that action functions use.
- The definition of FxGlobalFunctionCall_IsPointerEqual was not so big and
  scary, so this can't be called so much of an improvement as
  CheckClass was. (Which is not to say that it isn't better anyway.)

src/thingdef/thingdef_codeptr.cpp

@@ -152,6 +152,67 @@ bool ACustomInventory::CallStateChain (AActor *actor, FState *state)
 	return !!result;
 }
 
+//==========================================================================
+//
+// CheckClass
+//
+// NON-ACTION function to check a pointer's class.
+//
+//==========================================================================
+
+DEFINE_ACTION_FUNCTION(AActor, CheckClass)
+{
+	if (numret > 0)
+	{
+		assert(ret != NULL);
+		PARAM_PROLOGUE;
+		PARAM_OBJECT	(self, AActor);
+		PARAM_CLASS		(checktype, AActor);
+		PARAM_INT_OPT	(pick_pointer)		{ pick_pointer = AAPTR_DEFAULT; }
+		PARAM_BOOL_OPT	(match_superclass)	{ match_superclass = false; }
+
+		self = COPY_AAPTR(self, pick_pointer);
+		if (self == NULL)
+		{
+			ret->SetInt(false);
+		}
+		else if (match_superclass)
+		{
+			ret->SetInt(self->IsKindOf(checktype));
+		}
+		else
+		{
+			ret->SetInt(self->GetClass() == checktype);
+		}
+		return 1;
+	}
+	return 0;
+}
+
+//==========================================================================
+//
+// IsPointerEqual
+//
+// NON-ACTION function to check if two pointers are equal.
+//
+//==========================================================================
+
+DEFINE_ACTION_FUNCTION_PARAMS(AActor, IsPointerEqual)
+{
+	if (numret > 0)
+	{
+		assert(ret != NULL);
+		PARAM_PROLOGUE;
+		PARAM_OBJECT	(self, AActor);
+		PARAM_INT		(ptr_select1);
+		PARAM_INT		(ptr_select2);
+
+		ret->SetInt(COPY_AAPTR(self, ptr_select1) == COPY_AAPTR(self, ptr_select2));
+		return 1;
+	}
+	return 0;
+}
+
 //==========================================================================
 //
 // A_RearrangePointers