Round one of fixes to avoid ridiculous numbers of spurious copy constructor and destructor calls.

Most of these fixes involve calls to BOOST_FOREACH to iterate over a map or unordered_map where the
iterator type didn't perfectly match the internal type, so a reference into the map couldn't be created
and a new value/content pair had to be created for each iteration.

src/cpp/ripple/TransactionEngine.cpp

@@ -23,7 +23,7 @@ DECLARE_INSTANCE(TransactionEngine);
 void TransactionEngine::txnWrite()
 {
 	// Write back the account states
-	typedef std::pair<const uint256, LedgerEntrySetEntry> u256_LES_pair;
+	typedef std::map<uint256, LedgerEntrySetEntry>::value_type u256_LES_pair;
 	BOOST_FOREACH(u256_LES_pair& it, mNodes)
 	{
 		const SLE::pointer&	sleEntry	= it.second.mEntry;