pppd: Add support for EAP-MSCHAPv2 (client side) (#211)

pppd: Add support for EAP-MSCHAPv2 (client side) (#211)

* Adding EAP-MSCHAPv2 support #175

Implementation based on the RFC: draft-kamath-pppext-eap-mschapv2-02.
Adding support for MSCHAPv2 inside extensible authentication protocol (EAP).

Signed-off-by: Thomas Omerzu <thomas@omerzu.de>
* Removing empty "TODO" in comment section

Signed-off-by: Eivind Naess <eivnaes@yahoo.com>
* Add support for EAP-MSCHAPv2 #138

Rewrote the original patch to use the chap-new.c API for caching request/responses. Also incorporate feedback from @paulusmack for input validation and function signatures.

Signed-off-by: Eivind Naess <eivnaes@yahoo.com>
* Adding length checks per Paul's request

Signed-off-by: Eivind Naess, eivnaes@yahoo.com
Co-authored-by: Thomas Omerzu <thomas@omerzu.de>