Lib.pm: pass the output io handle to pre/post_output hooks
Lib.pm: clarify when the name prefix is added
Lib.pm: keep $frame[3] in a variable
Lib.pm: stop printing the (wrong) file:line
Lib.pm: fix wrong funcname in _die() output
Lib.pm: don't run $post_output for _die()
Lib.pm: merge _msg and _fmsg into one function
Lib.pm: port _err etc. to the new _msg
Lib.pm: various fixes
add `testlib.pl`
add `vimdiffdirs` (like vimdiff but recursive)