One more set of checkins before the next release. This one makes the ubd
driver fall back to synchronous I/O if it can't start the I/O thread. The
main reason this can happen is that the I/O thread communicates with the
kernel with a pts pty, which can't be allocated by a normal user on sme
distributions. So, not having a backup plan would make uml unusable for those
people without running as root.
I also changed arch/um/defconfig and bumped EXTRAVERSION in arch/um/Makefile.