update xrope
typedef struct pic_code pic_code
typedef struct pic_block pic_block
add missing find_package(git)
change native_stack marker type to char *
use pic_try/catch in stdlib_load
add pic_blk_exit
[bugfix] pic_close broken
Sort functions for lists

There are some bugs in merge-sort!.
[bugfix] merge-sort!

merge-sort! returns correct lists.
Sort functions for vectors are not implemented.
Merge pull request #66 from koba-e964/master

SRFI 95 Sorting and Merging
update readme
add koba-e to AUTHORS
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
list? for circular lists

pic_list_p() detects circular lists using Floyd's cycle-finding algorithm.
cleanup

Re-format the code so that it complies with the C coding rule of picrin.
Merge pull request #69 from koba-e964/master

list? for circular lists (Issue #17)