added takedrop
rm trailing whitespaces everywhere
added takedrop and its tests
added ntake
added ntake plus tests
corrected implementation of ntake
Merge pull request #416 from UnixJunkie/takedrop

BatList.takedrop & ntake
simpler partition code
Merge pull request #422 from UnixJunkie/simpler_partition

simpler List.partition implementation using accum helper
Add the new O_CLOEXEC flag to Unix.open_flag in version 4.1