Add sendfile(2).

This patch marks the end of OSFileSystem.

Having to support a Java "long*" for sendfile(2) gave me an opportunity to go
back and improve my ioctl(2) to use a corresponding "int*" equivalent, instead
of its previous special-case hack.

Bug: 3107501
Change-Id: I9fde4777700552263fab4fe9aeb556174163e3dc
27 files changed