move "scheme" collection to a "scheme-lib" package

Also, move remaining "srfi" libraries to "srfi-lite-lib".

In principle, "base" should depend on "scheme-lib" and
"srfi-lite-lib", and a new "base2" package would represent the new,
smaller base. But I don't think the window has yet closed on
determining the initial "base" package.

The "srfi" libraries moved to "srfi-lite-lib", instead of "srfi-lib",
to avoid creating many extra dependencies on "srfi-lib" and all of its
dependencies. The SRFIs in "srfi-lite-lib" depend only on "base",
and they are used relatively widely.

original commit: d175c3949c602672d61734b3fc54750da1d57f89

pkgs/gui-pkgs/gui-lib/info.rkt

@@ -10,6 +10,7 @@
                "snip-lib"
                "wxme-lib"
                "pict-lib"
+               "scheme-lib"
                "scribble-lib"
                "string-constants-lib"
                "unstable-list-lib" ; for class-iop