Add pipe2 and O_CLOEXEC to the libcore POSIX API.

@hide right now, but we should expose these at some point.

Bug: 18719692
Change-Id: I0a73606cf089ed307d1ab2916a7df28b3c45aaf0
Merge "Add pipe2 and O_CLOEXEC to the libcore POSIX API."
Fix native registration.

I thought I'd tested my previous change but hadn't.

Change-Id: Ie121b571cc2f767dd4bbe10291a56fe31496e6cc
Merge "Fix native registration."