I am not sure if you can also get the same hang in the periodic update list as well, but to be on the safe side added same checks as the one that was hanging.

Found the issue where it was freeing transfers from the follow up list, that were also on the QH list which also tried to free it again.

Fix was in the first free list, it checks to see if the item is also in the qh list and does not free it then.

This commit should start to allow some Prolific PL2303 devices to work.
Tis device has a rather more complex initialization process than some
of the other devices.

I have tested this some with one device that I used to use to program
some older RS232 based boards plus talk to an SSC-32 device.
Test case is I am able to talk to SSC-32 and if I type in ver<cr>
It does properly return the version number.

The data I am seeing is pretty close to what
was documented in: https://gist.github.com/tommie/89011c5ac06553d5cdb8
as well as what the Linux driver outputs.

I also incorperated Frank's configuration options.