Integrate with input formats module

Hi, I'm the maintainer of Input Formats module, I'm opening this issue because there are some settings of wysiwyg_filter that cannot be exported without a litter of help of you markus_petrux :)

You see, input formats obtains almost all the variables used by a filter module, iterating by the configuration form. However, some modules (like wysiwyg_filter) are defining extra variables, and the bad thing is, they are critical to get the filter working properly.

For this reason, I need filters modules that use this kind of variables implement a small hook to let know to input formats module which variables are needed to export all the filter settings properly.

As far I know, the only variable not defined in the config for is:

variable_set('wysiwyg_filter_valid_elements_parsed_'. $format, $valid_elements);

So this patch return this variable (without the _format suffix) with a description to let a chance to input formats export it too.

Thanks for reading.