Convert Presto, OpenJTAG and USB-Blaster (I) adapter drivers to libftdi
only.

Change-Id: Ib28887620a3dcbb754b9dbf87b9731acca3ac600
Signed-off-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>
Reviewed-on: http://openocd.zylin.com/3237
Tested-by: jenkins
Reviewed-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Reviewed-by: Freddie Chopin <freddie.chopin@gmail.com>

Also add further documentation about the project and how to use it.

Change-Id: Ia9878de566b3c8c1ea29f129287d5aea904d861d
Signed-off-by: Tim 'mithro' Ansell <mithro@mithis.com>
Reviewed-on: http://openocd.zylin.com/2961
Tested-by: jenkins
Reviewed-by: Paul Fertser <fercerpav@gmail.com>

adapter_init (core.c) won't check speed configuration
of the selected interface if it's not needed (.speed = NULL).

When it's not needed, we can now omit adapter_khz in
init scripts and we don't have to implement dummy handlers
for speed_div and khz functions.

It also removes calls to adapter_khz in interface configuration
files when not used anymore.

Change-Id: I6eb1894385503fede542a368f297cec6565eed44
Signed-off-by: Franck Jullien <franck.jullien@gmail.com>
Reviewed-on: http://openocd.zylin.com/1131
Tested-by: jenkins
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>

Globally rename "jtag_khz" as "adapter_khz", and move it out of the "jtag"
command group ...  it needs to be used with non-JTAG transports

Includes a migration aid (in jtag/startup.tcl) so that old user scripts
won't break.  That aid should Sunset in about a year.  (We may want to
update it to include a nag message too.)

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>

The 10-pin JTAG layout used with these adapters is used by
a variety of platforms including AVR.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>