Fixed wrong Context2d text baseline offset ajust

Fixed wrong Context2d text baseline offset ajust for "middle" and
"hanging" options.

Task-number: QTBUG-32463

Change-Id: Iad0b49bfc2129e008025ea7c6eb9e7d99ac7483d
Signed-off-by: Wesley Ceraso Prudencio <wesleyceraso@gmail.com>
Reviewed-by: Alan Alpert <aalpert@blackberry.com>
Reviewed-by: Yunqiao Yin <charles@mazymind.com>