Auto merge of #1058 - ebfull:coin-cache, r=ebfull

Flush to disk more consistently by accounting memory usage of serials/anchors in cache.

Closes #626.

It's important that this at least *approximates* the memory usage, so that we flush the cache to disk as expected. It's okay that we overestimate. The serials are stored in keys in the `boost::unordered_map`, so we can simply use that map's `DynamicMemoryUsage`. The anchors are another story.

src/test/coins_tests.cpp

@@ -136,7 +136,9 @@ public:
     void SelfTest() const
     {
         // Manually recompute the dynamic usage of the whole data, and compare it.
-        size_t ret = memusage::DynamicUsage(cacheCoins);
+        size_t ret = memusage::DynamicUsage(cacheCoins) +
+                     memusage::DynamicUsage(cacheAnchors) +
+                     memusage::DynamicUsage(cacheSerials);
         for (CCoinsMap::iterator it = cacheCoins.begin(); it != cacheCoins.end(); it++) {
             ret += memusage::DynamicUsage(it->second.coins);
         }