Avoid the hard coding of the maximum size for the registry value name
Avoid the hard coding of the maximum size for the registry value name

Build test run on Windows XP with Qt 4.7.2. No regressions found.

Change-Id: I19fc7a01c1a9b949ed998966210bde325987df9f
Reviewed-by: Denis Shienkov <1ad2dee90c89b865e4a01188e9919a005e3f77cf@yandex.ru>

kobolabs/qtserialport,RoadWorksSoftware/QtSerialPort-OS2,kobolabs/qtserialport,RoadWorksSoftware/QtSerialPort-OS2