MDL-36571 qtype multichoice: don't corrupt unicode characters.

MDL-36571 qtype multichoice: don't corrupt unicode characters.

It seems that \s includes non-breaking space, and the typical one-byte
representation of that is the same as some parts of multibyte unicode
characters. Therefore, you need to include the u modifer on the regular
expressions.

Also, remove any number of <br /> at the end of the answer.

Thanks to Joseph Rézeau and Jean-Michel Vedrine for working out what the
problem was, and how to fix it.