Adapt to work with GHC 6.12

- Adapted the package to work with GHC 6.12
- Plugins that depend on the old base3 are currently
  not correctly loaded as the plugin loaded misses
  the dependence on syb (leading to unresolved symbols)
- Cleaned up most of the testsuite (there are still
  some outstanding failures, of which only one
  demonstrates a bug in the plugins library as far
  as I can see — see previous bullet point)
- Cleaned out a little cruft (but more could be done)

Setup.lhs

@@ -2,4 +2,4 @@
 > module Main where
 > import Distribution.Simple
 > main :: IO ()
-> main = defaultMainWithHooks defaultUserHooks
+> main = defaultMainWithHooks autoconfUserHooks