Split collection names that come from specified collections on "/"s.

The code in "setup-cmdline.ss" makes sure that they all look like a
require specification, which means that they *are* separated by "/"s,
and not, for example, "\"s on windows.

svn: r15598

collects/setup/setup-unit.ss

@@ -379,8 +379,13 @@
       (if no-specific-collections?
         all-collections
         (check-again-all
-         (filter-map (lambda (c) (collection->cc (map string->path c)))
-                     x-specific-collections))))))
+         (filter-map
+          (lambda (c)
+            (collection->cc (append-map (lambda (s)
+                                          (map string->path
+                                               (regexp-split #rx"/" s)))
+                                        c)))
+          x-specific-collections))))))
 
   (set! planet-dirs-to-compile
         (sort-collections