Fix doc for nghttp2_select_next_protocol
Fix doc for nghttp2_select_next_protocol

We have to return this error code to notify OpenSSL that we have not
filled any values in |*out| and |*outlen|.

shines77/nghttp2,serioussam/nghttp2,icing/nghttp2,wzyboy/nghttp2,dxq-git/nghttp2,ohyeah521/nghttp2,thinred/nghttp2,shines77/nghttp2,syohex/nghttp2,lukw00/nghttp2,bxshi/nghttp2,wzyboy/nghttp2,mixianghang/nghttp2,shines77/nghttp2,ohyeah521/nghttp2,bxshi/nghttp2,serioussam/nghttp2,icing/nghttp2,yuki-kodama/nghttp2,syohex/nghttp2,wzyboy/nghttp2,serioussam/nghttp2,icing/nghttp2,kelbyludwig/nghttp2,yuki-kodama/nghttp2,thinred/nghttp2,ohyeah521/nghttp2,serioussam/nghttp2,serioussam/nghttp2,yuki-kodama/nghttp2,dxq-git/nghttp2,icing/nghttp2,dxq-git/nghttp2,wzyboy/nghttp2,yuki-kodama/nghttp2,minhoryang/nghttp2,thinred/nghttp2,kelbyludwig/nghttp2,minhoryang/nghttp2,yuki-kodama/nghttp2,thinred/nghttp2,mixianghang/nghttp2,dxq-git/nghttp2,thinred/nghttp2,kelbyludwig/nghttp2,serioussam/nghttp2,serioussam/nghttp2,lukw00/nghttp2,icing/nghttp2,mixianghang/nghttp2,bxshi/nghttp2,lukw00/nghttp2,bxshi/nghttp2,shines77/nghttp2,ohyeah521/nghttp2,minhoryang/nghttp2,mixianghang/nghttp2,dxq-git/nghttp2,syohex/nghttp2,wzyboy/nghttp2,syohex/nghttp2,bxshi/nghttp2,shines77/nghttp2,dxq-git/nghttp2,lukw00/nghttp2,minhoryang/nghttp2,kelbyludwig/nghttp2,yuki-kodama/nghttp2,mixianghang/nghttp2,mixianghang/nghttp2,syohex/nghttp2,syohex/nghttp2,bxshi/nghttp2,icing/nghttp2,wzyboy/nghttp2,kelbyludwig/nghttp2,thinred/nghttp2,shines77/nghttp2,icing/nghttp2,lukw00/nghttp2,minhoryang/nghttp2,kelbyludwig/nghttp2,thinred/nghttp2,minhoryang/nghttp2,ohyeah521/nghttp2,ohyeah521/nghttp2,wzyboy/nghttp2,lukw00/nghttp2,lukw00/nghttp2