Add builtin status

Created by: Sag0Sag0

New builtin, status.

Accepts three arguments. -l returns true if the shell is a login shell. -i returns true if the shell is interactive. -f prints the filename of the currently running shell script or if there is none prints stdio.

Potential problem status works out if the current shell is a login shell by checking that arg[0][0] == '-', that is the convention on unix based systems. However I'm unsure if redox does this.