table: clone, slice, keys, values. tuple: slice

add a couple of new table/tuple methods
use static for yet unused table methods
touch on tuple_clone, table_remove
add test/tables/slice.pn

JIT is still broken because of NYI optional sig-defaults
test/tables/slice.pn: use nil

fails JIT. not using print_0 branch yet
add ChangeLog

needed to track changes since 0.1
dist: add ChangeLog
Added methods for table: clone, slice, keys, values...

For tuple: slice. For bytes and string: clone
Added support for negative arguments for string.slice
Changed API's for potion_type_error_want
Merge branch 'slice'
print/say should return "" not nil

as in perl. "" is silent
print_0: adjust tests
print_0: file and lobby->say

file_print may also return PNError
print_0: fix test/tables/slice.pn