helper/command: disable logging of registered commands [RFC]

helper/command: disable logging of registered commands [RFC]

Every debug log of OpenOCD contains approximately 130 lines like:

Debug: 264 147 command.c:354 register_command_handler(): registering 'flash'...

Because only root name of the command is logged, most of lines is not
too informative. E.g. registering 'flash' is repeated 14 times.

Karl Passon submitted the patch [1] changing the logged cmd name from
root to lowest level. It makes the log better. Unfortunately we also have
'reset_config' and 'cortex_m reset_config' and similar which looks
equal in the log after [1].
Moreover [1] has not been reviewed for 5 years.

So my guess is that nobody uses that crap in debug log.

Save more than 10 kbytes in any debug log and make log analyse easier
by blocking log command in #if 0 block.
If some developer eventually needs to debug cmd registering he can easily
enable logging again.

[1] http://openocd.zylin.com/2765

Change-Id: Ib7e528aadd692fd0da2e3c005b4c5a484551b728
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: http://openocd.zylin.com/5928
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-by: Christopher Head <chead@zaber.com>