linux_udev: Log error code on pthread_create failure

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
hotplug: ensure udev monitor fd is non-blocking

Some older versions of udev do not automatically set the udev
monitor fd to non-blocking mode. This patch ensures that this is
always set.

HdG: Get flags then or in O_NONBLOCK and set them, rather then setting flags
to only O_NONBLOCK.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Merge branch 'master' of https://github.com/libusbx/libusbx