This matches what frameworks/base does with Build.VERSION and means that
bionic's version number will always sort >= than any released version.
This should prevent confusion in code that builds both against bionic
and the NDK.
(Note that <sys/cdefs.h> drags this in, so it's always in the namespace.)
Bug: 14613709
Change-Id: I91fb745920e848a6b20f2f5797c0a7d6cde6c032