usbscsi: Switch from lockdev to flock
usbscsi: Switch from lockdev to flock

Currently there are 2 problems with the lockdev usage in usbscsi:
1) It breaks usbscsi completely due to a missing symbol when dlopening
   usbscsi.so, which is caused by libgphoto2_port/usbscsi/Makefile-files not
   adding $(SERIAL_LIBS) to usbscsi_la_LIBADD
2) lockdev uses /var/lock/lockdev, which by default is:
   drwxrwxr-x. 2 root lock 40 Sep 19 22:49 /var/lock/lockdev
   So despite our udev rules, gphoto using apps need to run as
   root (or group lockdev) to be able to work with usbscsi port devices

I've decided to fix 2) by moving to flock, lockdev makes sense for serial
ports, since other programs may be trying to access them at the same time,
for usbscsi however we only need to coordinate with other apps also using
libgphoto2, and flock then suffices, is much simpler and does not have
the rights issues of lockdev. This fix for 2), also fixes 1) by simply no
longer needing lockdev.


git-svn-id: 40dd595c6684d839db675001a64203a1457e7319@14114 67ed7778-7388-44ab-90cf-0a291f65f57c

gphoto/libgphoto2.OLDMIGRATION,gphoto/libgphoto2.OLDMIGRATION,gphoto/libgphoto2.OLDMIGRATION,gphoto/libgphoto2.OLDMIGRATION