No problems reported other than Linus typo in an unbuildable driver from
the last one.

This one adds tty_ldisc_flush and also makes tty_wakeup do the queue
wake as discussed with Paul.  I've then propagated these functions
through all the drivers.  This means most drivers don't know about the
ldisc locking and instead call generic functions that look after it. 
The result is the removal of a lot of duplicate code both for ldisc
referencing and historical code for handling tty ldisc wakeup semantics.

A nice side effect is that by adding versions of the two helpers we can
switch most of the drivers over before changing the core tty code if
preferred.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>