This patch adds the functionality to the gdb-stub to single step with 
the IRQs and timers disabled.  It greatly improves gdb's ability to 
perform run control while running a linux kernel and stepping off of 
breakpoints or stepping into certain types of functions.  I have also 
included individual controls for IRQs and timers to restore the original 
behavior, since it is useful as well.

signed-off-by: jason.wessel@windriver.com

Jason.