[master] Update 3rd party licnese issues

    Instead of duplicating more third-party licenses here in LICENSE
    file (there are many), just generically suggest to see the other files.

    Per the md5 copyright license agreement, add mention of
    required verbatim advertising statement in the release notes and
    readme.

    In the RELNOTES, I also mention ISC is open source software.

    In the README, I added a HISTORY section and placed that
    advertising statement there. If the HISTORY section is not wanted,
    then remove it and just mention the required verbatim advertising statement.
    By the way, some good history is in old READMEs and at
    http://hack.org/mc/texts/dhcp-freenix.txt
    (but I can't find the official hosted Lemon version of that paper).

    Remove the advertising clause from the historical BSD
    code copyrighted by The Regents of the University of California.

    For details see
    ftp://ftp.cs.berkeley.edu/pub/4bsd/README.Impt.License.Change

    (To summarize: in 1999, the University said that distributors
    are no longer required to acknowledge within advertising and the
    paragraph in the license may be deleted.)

1 files changed, 3 insertions, 0 deletions

diff --git a/LICENSE b/LICENSE
index eef341e1..dc09c0aa 100644
--- a/LICENSE
+++ b/LICENSE
@@ -18,3 +18,6 @@
 #   Redwood City, CA 94063
 #   <info@isc.org>
 #   https://www.isc.org/
+
+See the specific source files for any additional copyright or
+license statements.