Change Cabal dep to >=1.2 now that the required patches are in the 1.2 branch....

Change Cabal dep to >=1.2 now that the required patches are in the 1.2 branch. This should really be >= 1.2.1, but the version number of the 1.2 has not been bumped yet.

cabal-install/cabal-install.cabal

@@ -37,7 +37,7 @@ Executable cabal
         Hackage.Update
         Hackage.Utils
 
-    build-depends: mtl, network, regex-compat, unix, Cabal>=1.3,
+    build-depends: mtl, network, regex-compat, unix, Cabal>=1.2,
                    zlib >= 0.4, HTTP >= 3000.0 && < 3000.1, filepath >= 1.0
 
     if flag(old-base) {