VFS: add ability to open files O_CLOEXEC

.adjust libc to make use of it (undo __minix diff)

Change-Id: I90a1aa219fcd1b12b6bc60e72176f326eac8184a
socket: implement SOCK_CLOEXEC and SOCK_NONBLOCK

Change-Id: I3fa36fa999c82a192d402cb4d913bd397e106e53
VFS: implement pipe2

Change-Id: Iedc8042dd73a903456b25ba665d12577f5589ca2
libc: drop Minix popen and use NetBSD's

Change-Id: I56f253d855671a6e1c8d53c7383107565164ab8d
test67: test opening files and sockets with O_CLOEXEC

Change-Id: If71e61f830c6d3b5154368e189baa4f70bd73850
test68: test pipe2 functionality

Change-Id: Idb15ec83983d0b052232c9533f89d637229d19df
Kernel: make shutdown more verbose

Change-Id: Iab5fed4cb617a9dbce164ff81c7dedf408e9fd98