sim: callback: add human readable strings for debugging to maps

sim: callback: add human readable strings for debugging to maps

When tracing, we often want to display the human readable name for the
various syscall/errno values.  Rather than make each target duplicate
the lookup, extend the existing maps to include the string directly,
and add helper functions to look up the constants.

While most targets are autogenerated (from libgloss), the bfin/cris
targets have custom maps for the Linux ABI which need to be updated
by hand.