Add (hidden) RFC license

[LeChasseur]

The database already contains LicenseRef-scancode-ietf . This seems to be the license for much IETF content but there are sometimes other licenses as well.
Example: Punicode (https://datatracker.ietf.org/doc/html/rfc3492) seems to be under LicenseRef-scancode-ietf which is indicated on the last page (https://datatracker.ietf.org/doc/html/rfc3492#page-35). This is not a FOSS license.
However, there is another license that covers the sample code: https://datatracker.ietf.org/doc/html/rfc3492#page-22
...
Disclaimer and license

Regarding this entire document or any portion of it (including the
pseudocode and C code), the author makes no guarantees and is not
responsible for any damage resulting from its use. The author grants
irrevocable permission to anyone to use, modify, and distribute it in
any way that does not diminish the rights of anyone else to use,
modify, and distribute it, provided that redistributed derivative
works do not contain misleading author or version information.
Derivative works need not be licensed under similar terms.
...
I haven't found an identifier for it. LicenseRef-scancode-ietf-rfc3492 might be suitable.

[DennisClark]

@AyanSinhaMahapatra I have added LicenseRef-scancode-ietf-rfc3492 to DejaCode. Permissive. Please synch the new definition and create corresponding detection rules, thanks!