Show short scriptPubKeys correctly

Previously bitcoin-qt's -debug transaction info was showing CTxOut([error])

It is valid for a scriptPubKey to be any size, for example simply
OP_RETURN is valid and can be used to destroy a TXOUT to mining fees.

Conflicts:
    src/core.cpp

Rebased-from: 5d37b9db291cf60d3a1b4a15d00ef00baa7d9f4e 0.8.x

src/main.h

@@ -450,8 +450,6 @@ public:
 
     std::string ToString() const
     {
-        if (scriptPubKey.size() < 6)
-            return "CTxOut(error)";
         return strprintf("CTxOut(nValue=%"PRI64d".%08"PRI64d", scriptPubKey=%s)", nValue / COIN, nValue % COIN, scriptPubKey.ToString().substr(0,30).c_str());
     }