repl.scm: fixed list-tail
ISSUES.md updated
repl.scm: unzip speed improvement
env.c: refactored new_frame_io()

new_frame_io() did a lot of things at once, splitting
walk-through-arguments into a function; some comments;
tests/andor.scm: works in Guile, requires `,@`
Touched tests/* to be in sync with repl