remove stray mode on callback, seems to not change anything
tidy version numbers and copyright dates
auto merge of #5667 : graydon/rust/remove-a-mode, r=catamorphism

It seems nobody can figure out whether this is _supposed to_ make a difference anymore, and in testing it seems to work either way, so I removed it. One less alarming warning during a fresh build.
auto merge of #5669 : graydon/rust/tweaks, r=thestinger

Just some minor cleanup of version strings and copyrights.