Display Cabal version in configure output with -v

eg "Using Cabal-1.5.1 compiled by ghc-6.8"
Annoyingly ghc doesn't give us its full version number.

Distribution/Simple/Configure.hs

@@ -432,6 +432,8 @@ configure (pkg_descr0, pbi) cfg
         unless (isAbsolute (prefix dirs)) $ die $
             "expected an absolute directory name for --prefix: " ++ prefix dirs
 
+        info verbosity $ "Using " ++ display currentCabalId
+                      ++ " compiled by " ++ display currentCompilerId
         info verbosity $ "Using compiler: " ++ showCompilerId comp
         info verbosity $ "Using install prefix: " ++ prefix dirs