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/FeatureTable.cpp

@@ -128,7 +128,7 @@ void FeatureTable::reportValidations(const FeatureSet& set)
 		return;
 	int threshold = (set.mTrustedValidations * mMajorityFraction) / 256;
 
-	typedef std::pair<const uint256, int> u256_int_pair;
+	typedef std::map<uint256, int>::value_type u256_int_pair;
 
 	boost::mutex::scoped_lock sl(mMutex);