Another missing ERR definition

Make use of Lib.time_to_string.

Support for evaluating instructions of the form "ldr pc,[pc,rn,lsl #2]".

Previously this would not work for certain registers "rn". This now works but a
precondition is added, namely: ARM_READ_REG rn state << 2 <> 0xFFFFFFF8w.
This ensures that the branch destination is not the machine-code value of the
instruction.

Fix problem with instructions of the form ldm <rn>!,{...,pc}^.

Base register write-back was happening in the wrong mode.

Change the specification wrt interrupt masking. The function arm_next no
longer masks interrupts -- this is instead left to the level above,
e.g. arm_run.

Other changes include more checking of step theorems in selftest. Also made use
of tools in updateLib.

Minor change to the predictability of the CPS instruction, to keep up with the
ARM Reference Errata 8.

Fix evaluation with regard to LDM/STM instructions with the base register in
the register list and write-back enabled.

In some places move the position of increment_pc (under operator |||).

Add a selftest program for ARM tools.

(NB. takes around 10 mins to run on my machine.)