Make random an "extra" package

It will get built as part of "validate --slow".  We have 11 tests that
depend on random, so this enables more tests to work.

packages

@@ -63,7 +63,7 @@ libraries/xhtml              -           -                               https:/
 nofib                        nofib       -                               -
 libraries/parallel           extra       -                               ssh://git@github.com/haskell/parallel.git
 libraries/stm                extra       -                               -
-libraries/random             dph         -                               https://github.com/haskell/random.git
+libraries/random             extra       -                               https://github.com/haskell/random.git
 libraries/primitive          dph         -                               https://github.com/haskell/primitive.git
 libraries/vector             dph         -                               https://github.com/haskell/vector.git
 libraries/dph                dph         -                               -