publish format function family
[bugfix] is_quote family don't stop when circular object is given
[workaround] write function now stops in a certain recursion depth
revert prev commit
fix segv in is_quote etc
add support for circular objects to write
add write-shared
refactor tagged expression checker
fix memory leak
update xhash
add write function in C level (must not enter into a infinite loop)
s/port_/write_/g
update readme
reformat readme
grammer fix
cleanup
add pic_raise_continuable
support nested comments
update readme. add support for block comments
remove old exports