DIRECTOR: Implement working of titleVisible property of window

[r41k0u]

This set of changes resolves the missing window properties mentioned in https://trello.com/c/g1BaUzXz/292-missing-window-properties

[djsrv]

It doesn't look like this will work properly if you do this:

set the title of window "test" to "foo"
set the titleVisible of window "test" to false
set the title of window "test" to "bar"
set the titleVisible of window "test" to true

after which the title "bar" should be visible.

Either Window should override setTitle to update _titleTemp, or setTitleVisible should instead be implemented on the superclass MacWindow and something similar can be done there (which I think is the cleaner option).

[djsrv]

This should be removed since it's no longer used.

[djsrv]

I'd rename this method to MacWindow::setTitleVisible and make Director's Window::setTitleVisible override it.

Also move the definitions for _titleVisible and isTitleVisible to MacWindow instead of Window to eliminate the need for the redundant _isTitleVisible.

[djsrv]

Once you make this method override MacWindow::setTitleVisible you can replace this line with MacWindow::setTitleVisible(titleVisible);

[mistydemeo]

This introduces a case where the function can return without returning a value, which clang flags as a warning:

    C++      engines/director/lingo/lingo-object.o
engines/director/lingo/lingo-object.cpp:534:1: warning: non-void function does not return a value in all control paths [-Wreturn-type]
}
^

[sev-]

Any updates? @r41k0u

[sev-]

Closing for the sake of #5067