Exit after a EOF is reached
Implement 'clr'
Rename the 'exit' internal function to 'quit'

This way we don't conflict with the cstdlib version of exit
Statically set the command.background poperty

Instead of dynamically determining this using a struct function we
should just set it on the command struct when parsing the command. This
also ensure the background flag will not be in the argv
Use C++ 0x