Wrap uname to enable glibc installs for kernel revisions >= 255
Wrap uname to enable glibc installs for kernel revisions >= 255

Fixes #4429, although we're not yet patching uname syscalls.
The key issue is that glibc's version arithmetic can result it in
interpreting revision>=255 as minor+1, which could in turn result in
glibc trying to use kernel features that don't actually exist.
If we find that applications are crashing with SIGSYS then we'll also
need an LD_PRELOAD hack like the one here:
https://gist.github.com/dnschneid/5c88a1802868c1be74d4debb5627c8c7

dnschneid/crouton,dnschneid/crouton,dnschneid/crouton,dnschneid/crouton,dnschneid/crouton,dnschneid/crouton