A simple attempt at a shell implemented in the C language.
For now the commands are:
 - help: this one.
 - quit: quits the shell.
 - exit: same as above.
 - environ: display environmental variables for the process.
 - echo <text>: echos the text back to stdout.
 - ls [dir]: lists files in a directory, if dir is not specified
             the current directory is listed.
 - dir [dir]: same as ls.
 - clr/clear: clears the screen and puts it in the top left corner,
             this does not work for all terminals.