drop an obsolete QChar::NoCategory enum value

drop an obsolete QChar::NoCategory enum value

there is no such category in the Unicode specs. the QChar::NoCategory
was a subject of bugs since it was introduced. int 4.6 it's meaning was
limited to mention ucs4 > UNICODE_LAST_CODEPOINT only (which is useless anyways)
in order to preserve the old (wrong) behavior.
fix it now for qtbase

Change-Id: I630534824e071090b39772881e747c1fdb758719
Reviewed-on: http://codereview.qt.nokia.com/1584
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>