Mention xristos in AUTHORS
lua-send-region: send extra printline

This avoids putting interpreter output onto the prompt line.
Redo handling of "stdin:N" in tracebacks

The regexp that disabled highlighting of "stdin:N" turned out to be
overly magical (unstable, any change in it caused breakage).

This change enables highlighting back and adds advices around
compilation-mode functions to ensure minimum inconvenience: now any
"stdin:N:" message at line L points to line L of REPL buffer.