Introduce QChar::JoiningType enum and QChar::joiningType() method

This aimed to disctinct joining types "L", "T", and "U" from just "U".
Unicode 6.3.0 has introduced a character with joining type "L" and
Unicode 7.0 will add a few more characters of joining type "L", so
we'll have to deal with it anyways.

[ChangeLog][QtCore][QChar] Added JoiningType enum and joiningType()
 method that deprecates the old QChar::Joining enum and joining() method.

Change-Id: I4be3a3f745d944e689feb9b62d4ca86d1cf371b0
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>