erts: Lock file object in vfprintf
erts: Lock file object in vfprintf

This prevents garbled output when interleaved with fprintf or
similar, which often happened when crash dumping. The following
command is an easy way to reproduce the issue:

    erl -eval foo bar

bjorng/otp,vinoski/otp,aboroska/otp,dumbbell/otp,erlang/otp,emacsmirror/erlang,getong/otp,mikpe/otp,dumbbell/otp,kvakvs/otp,kvakvs/otp,g-andrade/otp,isvilen/otp,potatosalad/otp,electricimp/otp,jj1bdx/otp,isvilen/otp,emacsmirror/erlang,g-andrade/otp,mikpe/otp,ferd/otp,g-andrade/otp,ferd/otp,dgud/otp,uabboli/otp,aboroska/otp,vladdu/otp,isvilen/otp,rlipscombe/otp,vinoski/otp,getong/otp,electricimp/otp,getong/otp,bjorng/otp,aboroska/otp,emacsmirror/erlang,aboroska/otp,vladdu/otp,vladdu/otp,bjorng/otp,vinoski/otp,isvilen/otp,erlang/otp,mikpe/otp,dgud/otp,rlipscombe/otp,lrascao/otp,bjorng/otp,isvilen/otp,vinoski/otp,mikpe/otp,potatosalad/otp,rlipscombe/otp,potatosalad/otp,erlang/otp,isvilen/otp,erlang/otp,rlipscombe/otp,bjorng/otp,g-andrade/otp,dgud/otp,dumbbell/otp,rlipscombe/otp,lrascao/otp,emacsmirror/erlang,isvilen/otp,vladdu/otp,lrascao/otp,kvakvs/otp,uabboli/otp,jj1bdx/otp,uabboli/otp,mikpe/otp,bjorng/otp,electricimp/otp,vladdu/otp,ferd/otp,potatosalad/otp,electricimp/otp,jj1bdx/otp,rlipscombe/otp,kvakvs/otp,kvakvs/otp,vinoski/otp,dumbbell/otp,emacsmirror/erlang,aboroska/otp,getong/otp,potatosalad/otp,lrascao/otp,ferd/otp,vinoski/otp,potatosalad/otp,ferd/otp,jj1bdx/otp,erlang/otp,electricimp/otp,electricimp/otp,rlipscombe/otp,dumbbell/otp,uabboli/otp,ferd/otp,getong/otp,jj1bdx/otp,erlang/otp,erlang/otp,dgud/otp,g-andrade/otp,kvakvs/otp,ferd/otp,dumbbell/otp,vladdu/otp,isvilen/otp,jj1bdx/otp,mikpe/otp,g-andrade/otp,aboroska/otp,dgud/otp,electricimp/otp,jj1bdx/otp,g-andrade/otp,kvakvs/otp,potatosalad/otp,uabboli/otp,emacsmirror/erlang,potatosalad/otp,bjorng/otp,g-andrade/otp,vinoski/otp,uabboli/otp,ferd/otp,aboroska/otp,rlipscombe/otp,potatosalad/otp,dumbbell/otp,kvakvs/otp,g-andrade/otp,dgud/otp,getong/otp,dgud/otp,bjorng/otp,isvilen/otp,ferd/otp,jj1bdx/otp,erlang/otp,vladdu/otp,emacsmirror/erlang,jj1bdx/otp,emacsmirror/erlang,getong/otp,emacsmirror/erlang,g-andrade/otp,vinoski/otp,lrascao/otp,getong/otp,dgud/otp,getong/otp,uabboli/otp,dumbbell/otp,dgud/otp,aboroska/otp,vladdu/otp,uabboli/otp,dgud/otp,isvilen/otp,lrascao/otp,lrascao/otp,lrascao/otp,erlang/otp,jj1bdx/otp,rlipscombe/otp,vinoski/otp,mikpe/otp,electricimp/otp,mikpe/otp,dumbbell/otp,bjorng/otp,potatosalad/otp,mikpe/otp,emacsmirror/erlang,mikpe/otp,getong/otp,rlipscombe/otp,lrascao/otp,vladdu/otp,dumbbell/otp,vinoski/otp,electricimp/otp,aboroska/otp,bjorng/otp,uabboli/otp,kvakvs/otp,erlang/otp