(byte-compile-current-group): New var.

(byte-compile-current-group): New var.
(byte-compile-file): Bind it.
(byte-compile-nogroup-warn): Use it to avoid spurious warnings when the
group argument is provided implicitly.
(byte-compile-format-warn, byte-compile-from-buffer)
(byte-compile-insert-header): Don't hardcode point-min==1.
(byte-compile-file-form-require): Remove unused var old-load-list.
(byte-compile-eval): Remove unused vars old-autoloads and hist-nil-new.