Add uncommited generation checking to all the gen tasks.

If checking="true" on them, they generate their code to a String instead of a file, and compare that
against existing output.  If any generation would produce changes, the build is failed.

As a side effect, generation will now only write files if it's going to modify them, which should
eliminate some spurious compiling.



git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@6349 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/cpp/presents/data/ClientObject.h

@@ -5,7 +5,6 @@
 #include "presents/ObjectOutputStream.h"
 #include "presents/streamers/StreamableStreamer.h"
 
-#include "presents/data/PermissionPolicy.h"
 #include "presents/dobj/DObject.h"
 #include "presents/dobj/DSet.h"
 #include "util/Name.h"
@@ -18,7 +17,6 @@ public:
 
     Shared<util::Name> username;
     Shared<presents::dobj::DSet> receivers;
-    Shared<presents::data::PermissionPolicy> permPolicy;
 
     virtual void readObject(ObjectInputStream& in);
     virtual void writeObject(ObjectOutputStream& out) const;