Backport the inlines for cfsetspeed and tcdrain.

This fixes some issues with using boost's asio (which wrongly assumes
_BSD_SOURCE implies that these things are available) following our
change from -isystem to --sysroot.

Test: Manual, check that we can build when using cfsetspeed on ICS.
Bug: https://github.com/android-ndk/ndk/issues/302
Change-Id: Iab50221e4864f9a09a8fb00691252170eb6e8d09