sim:epiphany: Better error handling in epiphany-elf-sim

If a child dies before forking send SIGTERM to the parent
(epiphany-elf-sim) so that it aborts immediately.

Remove some unnecessary newlines from error reporting.

Handle permission denied on creating redirect_dir better.
sim:epiphany: epiphany-elf-sim: Fix python3 compatibility

Use octal numbering syntax supported by Python 3.
Script should work with python 2.7-3.3 now.