[Builder] Does not work with UTF8 chars

[gitahz]

Builder uses :element-type 'base-char for some arrays. With SBCL (2.5.0.0) this results in an exception when any text uses UTF chars.

Steps to reproduce:

1. Create a new panel project from a template
2. Add a DIV-element to the panel.
3. Write "über" into the text field of the DIV-element (without quotation marks). (Hint: "über" is from german and means "above")
4. Leave the text field. This should show up the text in the preview window.
5. Press the "Test" button in the preview window. This triggers the fault.