Fix for bug 178594, now katepart determinates the direction of each paragraph (line) according to the first strong character.

Since we are no longer using counting chars and not using QString::isRightToLeft() (we use a new internal implementation, based of QString::updateProperties()) we might have a small speed improvement: now determinating the paragraph direction is done (on average) in O(1) instead of O(n) - where n is the length of the string.