the properties to modify.
the name of the property to modify.
the new value of the property, or NULL to delete the property.
true on success or false on failure; call SDL_GetError for more information.
Threadsafety: It is safe to call this function from any thread.
Set a string property in a group of properties.
This function makes a copy of the string; the caller does not have to preserve the data after this call completes.