target: add examine-fail event

target: add examine-fail event

A configuration script may want to check the reason why examine fails
e.g. device has security lock engaged.

tcl/target/kx.cfg and klx.cfg is modified to use the new event
for testing of the security lock of Kinetis MCU

Change-Id: Id1d3a79d24e84b513f4ea35586cd2ab0437ff9b3
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: http://openocd.zylin.com/4289
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>