Fix job tracking in background jobs.
Refactor background jobs and builtins.
Handle SIGINT.
A simple shell. See grammar.ebnf for details about the parser.
Make sure you have GNU Readline installed and compile with make. By
default, it is compiled with -DDEBUG, which makes it print the AST
after each command. To disable this, compile with make DEFS="".
To exit out of the shell type use C-d.
See COPYING.