This is a replacement and extension of the patch
titled:
"[PATCH] sg: retrofit SG_FLAG_Q_AT_TAIL flag"

The aim is to give control over midlevel queuing
when commands are submitted via the sg, bsg and
the block layer SG_IO ioctl pass-throughs. The
current defaults remain: sg and bsg queue at_head
while the block layer SG_IO ioctl queues at_tail .
This patch allows user space programs that care to
override the default queuing for the sg driver and
the block layer SG_IO ioctl. The bsg driver already
has this capability.

This patch is against lk 2.6.33

Changelog
   - add SG_FLAG_Q_AT_TAIL and add SG_FLAG_Q_AT_HEAD
     flags to sg.h
   - act on these flags in the sg driver and the
     block layer SG_IO ioctl
   - correct stale urls in the sg driver code

Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>