Added new fixfiles -C PREVIOUS_FILECONTEXT  (RESTORE | CHECK)

Which will take an old version of the file_context file and the 
currently installed one and do a
diff.  Then it will run a recursive restorecon on all files covered by 
the difference.  The idea here
is to potentially call this function from within policy spec files on 
updates.  So the if the file_context
file changes on update, the file context on disk will be updated.

Also changed restorecon to not error out if one of the files  handed to 
it does not exist.

restorecon /etc/BOGUS_FILE /etc/passwd /etc/shadow

Will restore password and shadow and warn about BOGUS_FILE.

Dan