removeClass() glues class names together

I noticed that the removeClass() function in drupal.js does also remove spaces between two class names. The attached patch fixes that by replacing the class with leading and or trailing spaces with $1 instead of an empty string (you could also use $2). If $1 is empty, the class that should be removed is at the beginning of the className string, thus it doesn't matter if the trailing space is also removed. Same goes for the end. Only if the class is somehwere in the middle, a space is left to separate the two neighboring classes.