merge from another 1.3.1
Fix for http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=680146
Don't mark the following AVPs as mandatory:
  - Firmware Revision
  - Vendor name
  - Rx Connect speed
  - Physical channel ID

(from https://github.com/richvdh/xl2tpd/commit/af60a268dd590456c0e0a16da745e1ce748e13d7)
Merge remote-tracking branch 'tphelps/master' into testing
Merge remote-tracking branch 'floppym/master' into testing
Merge remote-tracking branch 'sigwall/kernel' into testing
Quash more valgrind warnings.

Valgrind warns that not all fields in the sockaddr_pppol2tp struct are
getting initialized.  Use memset to ensure that everything not explicitly
set will be cleared to zero, which should ensure that this continues to work
even if Linux adds new fields to the struct.
Merge pull request #12 from tphelps/valgrind

Fix valgrind warnings in testing branch