safe_asterisk: Overwrite old safe_asterisk on make install.

From now on, make install will overwrite safe_asterisk with the
latest version. You need to move any local modifications to files
inside /etc/asterisk/startup.d, if you have any.

See also commits r394939 and r397938.

ASTERISK-21965 #close
Patches:
  safe_asterisk.patch uploaded by jkister (License 6232, modified by me)


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@415748 f38db490-d61c-443f-a65b-d21fe96a405b