wheelScrollLines configuration option is ignored

no matter what value is given for the configuration option "qt/wheelScrollLines", it always results in the default value of "3" being set.

this can be easily tested with qtconfig (but all qt applications are affected):

1. Go to the "Interface" tab of qtconfig.
2. Change the value of "Wheel Scroll Lines" to something other than "3".
3. Save the new settings, and close qtconfig.
4. Re-open qtconfig - the "Wheel Scroll Lines" setting will be put back to "3".

Note that the other settings work as expected, and qtconfig does correctly write all the values to the config file. But for some reason, the "Wheel Scroll Lines" option is always ignored.

Also note that essentially the same thing happens if the config file is edited manually, and a different qt application is opened - the application ignores the config setting and always uses a wheelScrollLines value of "3".