Update hofstadter-sequences.lsp

Changes:
1) Hofstadter-Q has been changed for test purposes (it is now a
function, needs to be reverted as a macro ASAP).
2) Hofstadter-Pinn F sequences added (as hofstadter-pinn function). The
generalized formula needs to be checked. It works for default (0, 1)
value, the most interesting but also the most boring function of the
family (boring as in "Already explored a lot").