What package are feature names resident in?

[David A. Moon <Moon@SCRC-STONY-BROOK.ARPA>]

I'd like to revise my proposal to be that the "feature expression" after a
#+ or #- is read in the keyword package if no explicit package prefix
appears in it, but it is legal to use an explicit package prefix.  I also
propose that features defined in the Common Lisp manual be in the keyword
package, and "public" features (such as those of a particular implementation)
be in the keyword package, by convention.  "Private" features can be qualified
with a package name when that convention seems appropriate.  I also endorse
KMP's proposal that package failure while reading a feature name is
equivalent to nonpresence of that feature, rather than being an error.
Thus (list 1 #+(not nosuchpackage:quux) 2 3) evaluates to a list of 3
elements in most circumstances.