[ruby-core:26303] IO.foreach (and friends) effect on $< and $.

I have a few questions about how the line-by-line IO operations are
*supposed* to affect the ARGF global $< and the line number global $.

First off, it seems a bit inconsistent whether $< should be updated
for non-ARGF line iterations:

~/projects/jruby =E2=9E=94 ruby -v -e 'p $<.lineno; IO.foreach("build.xml")
{}; p $<.lineno'
ruby 1.8.6 (2008-08-11 patchlevel 287) [universal-darwin9.0]
0
1775

~/projects/jruby =E2=9E=94 ruby1.8.7 -v -e 'p $<.lineno;
IO.foreach("build.xml") {}; p $<.lineno'
ruby 1.8.7 (2009-09-11 patchlevel 202) [i686-darwin9.8.0]
0
1775

~/projects/jruby =E2=9E=94 ruby1.9 -v -e 'p $<.lineno; IO.foreach("build.xm=
l")
{}; p $<.lineno'
ruby 1.9.2dev (2009-07-23 trunk 24248) [i386-darwin9.7.1]
0
0

It seems like 1.9 is "correct" here. JRuby acts like 1.8 regardless of
1.8 or 1.9 mode.

Second, the $. variable. It appears to be consistently updated for all
Ruby versions, but I wonder whether it's useful if it isn't
thread-local. Thread-local would be better because multiple threads
iterating lines would not all be setting the same variable.

- Charlie