Suppress statement not reached warnings after noreturn functions

Suppress statement not reached warnings after noreturn functions

Use the AFS_UNREACHED macro to suppress statement not reached warnings while
building under Solaris Studio.  These warnings are emitted for statements
following functions declared with the noreturn function attribute.

Change-Id: Ic18cbb3ea78124acbe69edc0eccb2473b46648fe
Reviewed-on: https://gerrit.openafs.org/13010
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>