LIB-45: also try /dev/cdrom1 on Linux

Current Debian and Ubuntu releases don't seem to create /dev/cdrom
anymore, but only /dev/cdrom1, /dev/cdrom2 etc.

This should fix most cases when the actual device doesn't change.
When devices really change we could start analyzing
/proc/sys/dev/cdrom/info.
LIB-45: add another default device possibility

This device name was found on a SunOS 5.10 = Solaris 10.
create and use mb_disc_unix_find_devices()

instead of duplicating code
LIB-45: check both device names on FreeBSD
LIB-45: try both device names on NetBSD/OpenBSD

Additionally re-add the information to the FreeBSD device names.
fix typo on Linux drive candidates
LIB-45: parse /proc/sys/dev/cdrom on Linux

This extracts the default drive from /proc and falls back to
one of the hard coded defaults if this isn't available,
for the error message.

We might rather want to prefer /dev/cdrom, but that needs
fiddling with find_drive/exists in unix.c again.
LIB-45: prefer /dev/cdrom on Linux if available
Use strtok_r for thread-safety

Signed-off-by: Sebastian Ramacher <sramacher@debian.org>
Make default_device thread-local

Signed-off-by: Sebastian Ramacher <sramacher@debian.org>
Name the define THREAD_LOCAL and define it in every case

Signed-off-by: Sebastian Ramacher <sramacher@debian.org>
ChangeLog for LIB-48
Merge branch 'default_drive_exists'

see pull request #24 and LIB-45
Update ChangeLog for LIB-45

also fix a typo