Fix struct stat to match POSIX 2008.

Our representation of sub-second times matched the Linux kernel, and we
provided macros for glibc source compatibility. This change switches us
over to match POSIX 2008, adds the macros they insist on (for compatibility
with earlier versions of POSIX), and also adds macros for compatibility
with any code that expects the kernel or old bionic names.

Unfortunately this breaks strace which defines its own structures using
the kernel names, and thus implicitly assumes that there are no macros with
those names, but this does allow the rest of the tree to build.

Bug: 18298106
Change-Id: Ibfa8c21cb2a2566091ef3dc2019a9f78d2de2991