"unset" return value wrong

[Stephen Gildea]

The exit status of the "unset" shell built-in should be 0 if given any
unsettable variable, whether or not the variable needed to be unset.

In bash 2.04, unset returns 1 if the variable wasn't set to begin with.
This isn't the correct criterion according to Posix, and it broke a
shell script of mine that didn't expect that behavior.

Furthermore, "help unset" claims that PATH and IFS cannot be unset.
After reading that, I would expect "unset PATH" to not unset PATH and
to return 1.  Instead it does unset PATH and returns 0.

 < Stephen