Patch to allow for the submission of forms which have field names containing array indices

I'm trying to configure the Wysiwyg module for my site via the
pattern tag and have come up on an issue. The form values which need to be set have the following field name:

formats[1][editor] = ...

In the
tag the XML would look as follows:

But of course the <1> tag is invalid in XML. To workaround this issue I've patched system.inc such that you can write the above as follows:

The patch code will trim off '__' edges from the tag name once it has been loaded into memory as an array. It uses regular expression matching so other uses of the underscore in tag names won't be affected.