QChar: optimize some methods a bit for general case

QChar: optimize some methods a bit for general case

by reordering and regrouping conditions so that they lead to result earlier
in most-common usecases (l.letters, spaces and puncts, u.letters, other);
there are no title cased letters in range [0..127] -> use this in isTitleCase();
test for 0xa0 (nbsp) early in isSpace() as it is quite common in HTML, etc.;
add early test to isNumber().

Change-Id: Ib415f34cb1212d9ccf8753de2d1beaece1aa2243
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>