Issue 21: package of #+/#- features

[David A. Moon <Moon at SCRC-TENEX>]

I'd like to change my vote from "neutral" to "read features in the same
package as anything else, and put the features associated with the standard
language in the LISP package so they can be typed without prefixes."

In the Maclisp world features are sometimes used to simulate what Common
Lisp does with PROVIDE and REQUIRE.  I'm not completely sure, but I believe
that this won't work anymore if feature symbols are subject to packages.
However, I think PROVIDE and REQUIRE are a more reasonable way to do it.