Fix decode undef
Fix decode undef

Function avp/5 isn't exported from dictionary modules. Not necessarily
intentional, but don't just export it since that requires recompilation
of all dictionary modules, since the function is in diameter_gen.hrl.
Not having to recompile was the main motivation for moving most of the
included code to module diameter_gen in commit 205521d3.

This reveals a weakness in the decode of answers setting the E-bit: any
AVP that isn't defined by the common application won't be decoded; the
diameter_avp records that these are packed into (in the 'AVP' field of a
message record, or equivalent) will have value = undefined. This is
nothing new (same in OTP 19), but the values should be decoded. Fix it
(and the lack of test coverage) in a subsequent commit that will add
avp_dictionaries config.

rlipscombe/otp,emacsmirror/erlang,rlipscombe/otp,mikpe/otp,fenollp/otp,vladdu/otp,dgud/otp,bsmr-erlang/otp,vladdu/otp,vinoski/otp,kvakvs/otp,electricimp/otp,isvilen/otp,fenollp/otp,bernardd/otp,erlang/otp,aboroska/otp,lrascao/otp,mikpe/otp,dumbbell/otp,saleyn/otp,potatosalad/otp,dgud/otp,aboroska/otp,ferd/otp,dgud/otp,goertzenator/otp,legoscia/otp,cobusc/otp,goertzenator/otp,kvakvs/otp,dgud/otp,getong/otp,ferd/otp,dgud/otp,RaimoNiskanen/otp,mikpe/otp,dgud/otp,fenollp/otp,matwey/otp,aboroska/otp,falkevik/otp,fenollp/otp,getong/otp,RaimoNiskanen/otp,cobusc/otp,bernardd/otp,erlang/otp,potatosalad/otp,getong/otp,electricimp/otp,matwey/otp,cobusc/otp,bsmr-erlang/otp,matwey/otp,dumbbell/otp,kvakvs/otp,g-andrade/otp,potatosalad/otp,erlang/otp,vinoski/otp,dumbbell/otp,rlipscombe/otp,dumbbell/otp,lrascao/otp,bsmr-erlang/otp,bsmr-erlang/otp,rlipscombe/otp,rlipscombe/otp,uabboli/otp,dumbbell/otp,fenollp/otp,dgud/otp,saleyn/otp,isvilen/otp,bernardd/otp,emacsmirror/erlang,goertzenator/otp,ferd/otp,cobusc/otp,legoscia/otp,rlipscombe/otp,ferd/otp,matwey/otp,potatosalad/otp,vinoski/otp,saleyn/otp,saleyn/otp,bernardd/otp,jj1bdx/otp,bernardd/otp,isvilen/otp,aboroska/otp,bjorng/otp,isvilen/otp,emacsmirror/erlang,RoadRunnr/otp,mikpe/otp,getong/otp,jj1bdx/otp,vinoski/otp,g-andrade/otp,potatosalad/otp,g-andrade/otp,cobusc/otp,vladdu/otp,electricimp/otp,jj1bdx/otp,kvakvs/otp,legoscia/otp,electricimp/otp,vinoski/otp,dumbbell/otp,tuncer/otp,uabboli/otp,ferd/otp,emacsmirror/erlang,falkevik/otp,getong/otp,vladdu/otp,vladdu/otp,emacsmirror/erlang,falkevik/otp,electricimp/otp,falkevik/otp,vladdu/otp,dgud/otp,bernardd/otp,tuncer/otp,falkevik/otp,potatosalad/otp,vladdu/otp,isvilen/otp,RaimoNiskanen/otp,RoadRunnr/otp,mikpe/otp,rlipscombe/otp,bjorng/otp,aboroska/otp,tuncer/otp,ferd/otp,tuncer/otp,erlang/otp,tuncer/otp,potatosalad/otp,RaimoNiskanen/otp,g-andrade/otp,vinoski/otp,RaimoNiskanen/otp,kvakvs/otp,isvilen/otp,aboroska/otp,electricimp/otp,goertzenator/otp,RoadRunnr/otp,RoadRunnr/otp,uabboli/otp,RaimoNiskanen/otp,goertzenator/otp,bsmr-erlang/otp,electricimp/otp,lrascao/otp,uabboli/otp,aboroska/otp,potatosalad/otp,mikpe/otp,RoadRunnr/otp,lrascao/otp,saleyn/otp,dumbbell/otp,vinoski/otp,potatosalad/otp,erlang/otp,isvilen/otp,saleyn/otp,emacsmirror/erlang,saleyn/otp,vladdu/otp,lrascao/otp,emacsmirror/erlang,erlang/otp,bsmr-erlang/otp,g-andrade/otp,goertzenator/otp,uabboli/otp,fenollp/otp,bjorng/otp,tuncer/otp,isvilen/otp,rlipscombe/otp,aboroska/otp,bsmr-erlang/otp,RoadRunnr/otp,falkevik/otp,cobusc/otp,falkevik/otp,kvakvs/otp,dgud/otp,bsmr-erlang/otp,lrascao/otp,RaimoNiskanen/otp,goertzenator/otp,cobusc/otp,getong/otp,vinoski/otp,mikpe/otp,matwey/otp,tuncer/otp,RoadRunnr/otp,getong/otp,jj1bdx/otp,jj1bdx/otp,bjorng/otp,jj1bdx/otp,fenollp/otp,emacsmirror/erlang,g-andrade/otp,vinoski/otp,kvakvs/otp,legoscia/otp,matwey/otp,electricimp/otp,uabboli/otp,RoadRunnr/otp,tuncer/otp,jj1bdx/otp,goertzenator/otp,RoadRunnr/otp,g-andrade/otp,lrascao/otp,vinoski/otp,bjorng/otp,emacsmirror/erlang,RaimoNiskanen/otp,erlang/otp,dumbbell/otp,ferd/otp,dumbbell/otp,legoscia/otp,fenollp/otp,uabboli/otp,falkevik/otp,rlipscombe/otp,rlipscombe/otp,uabboli/otp,bjorng/otp,mikpe/otp,bjorng/otp,mikpe/otp,RaimoNiskanen/otp,lrascao/otp,falkevik/otp,jj1bdx/otp,legoscia/otp,electricimp/otp,matwey/otp,g-andrade/otp,getong/otp,saleyn/otp,matwey/otp,potatosalad/otp,dgud/otp,ferd/otp,kvakvs/otp,kvakvs/otp,tuncer/otp,aboroska/otp,bjorng/otp,getong/otp,saleyn/otp,dumbbell/otp,legoscia/otp,isvilen/otp,mikpe/otp,bernardd/otp,bjorng/otp,getong/otp,g-andrade/otp,ferd/otp,matwey/otp,lrascao/otp,jj1bdx/otp,cobusc/otp,erlang/otp,goertzenator/otp,legoscia/otp,erlang/otp,uabboli/otp,bernardd/otp,fenollp/otp,bjorng/otp,legoscia/otp,erlang/otp,isvilen/otp,jj1bdx/otp,vladdu/otp,g-andrade/otp,bernardd/otp,emacsmirror/erlang,bsmr-erlang/otp