See NEVERALLOW CHECKING in tools/README for documentation.

Depends on change I45b3502ff96b1d093574e1fecff93a582f8d00bd
for libsepol to support reporting all neverallow failures.

Change-Id: I47c16ccb910ac730c092cb3ab977c59cb8197ce0
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>