Including glibc's <libgen.h> will result in the user getting the POSIX
version of basename always, regardless of when it is included relative
to <string.h>. Prior to this patch, our implementation would result in
the one that's included first winning.
Bug: http://b/25459151
Change-Id: Id4aaf1670dad317d6bbc05763a84ee87596e8e59
Josh Gao