Garbled text on SMP systems

[sthibaul]

Copied over from bytefire/speakup#8

From TODO file:

"Another issue seems to only happen on SMP systems. It seems
that text in the output buffer gets garbled because a lock is not set.
This bug happens regularly, but no one has been able to find a situation
which produces it consistently."

Also this thread on speakup mailing list provides relevant information about this bug: http://linux-speakup.org/pipermail/speakup/2019-March/061660.html

This is fairly important as it hinders people from using speakup.