Updated Debuging for gdb python

Debug/NuttX: -> changed name of tcb struct to match current name

Debug/NuttX.py: -> existing code runs with python 3.4 (in gdb), added some other modules:

"show tcb": shows the full tcb at the given address
"show check_stack": shows the sorted stack of all currently running processes
"show regs": print registers for a pcb nr
"show alltcb": show all pid's with process names--> show tasks used to miss out on at least one task
"show mybt": as the gdb bt would not work, this is a naive backtrace given for a tcb address