cleanup
refine pic_load error message
load srfi files at init. close #61
[bugfix] could not explicitly disable readline on some environment where libreadline
is installed
Merge pull request #69 from koba-e964/master

list? for circular lists (Issue #17)
refactor pic_list_p
pic_list_p don't need to take pic_state *.
pic_length is now unsafe to circular list
[bigfix] circular-list?

Fix a bug in circular-list?
[bugfix] circular-list? in srfi-1

circular-list? does not get stuck in an infinite loop if it is given a list such as '(1 2 3 2 3 2 3 2 3 ...).