Updates to Haskell bindings (#667)

* [haskell] Added uc_context_* support

As per issue #662

* [haskell] Updated bindings for commit 4083b87032

Updated for introduction of UC_HOOK_MEM_READ_AFTER.

* [haskell] Style fixes

bindings/haskell/src/cbits/unicorn_wrapper.c

@@ -6,3 +6,7 @@ void uc_close_wrapper(uc_engine *uc) {
 
 void uc_close_dummy(uc_engine *uc) {
 }
+
+void uc_context_free_wrapper(uc_context *context) {
+    uc_context_free(context);
+}