Add a new function reorder_kernel() that relinks and installs the

Add a new function reorder_kernel() that relinks and installs the
new kernel in the background on system startup. It stores the hash
of the new kernel and sends a notification email to the admin or
root user. If it finds /usr/share/compile.tgz, it removes the
existing compile dir and replaces it with the content of (new)
archive. If the hash of /bsd does not match the stored one, no
relinking happens.

Idea from, joint work with and OK deraadt@
OK tb@ halex@
unnoticed by many