Use range-based for loops (C++11) when looping over map elements

Before this commit:

  for (std::map<T1, T2>::iterator x = y.begin(); x != y.end(); ++x) {
  }

After this commit:

  for (auto& x : y) {
  }

src/qt/bantablemodel.cpp

@@ -55,11 +55,11 @@ public:
 #if QT_VERSION >= 0x040700
         cachedBanlist.reserve(banMap.size());
 #endif
-        for (banmap_t::iterator it = banMap.begin(); it != banMap.end(); it++)
+        for (const auto& entry : banMap)
         {
             CCombinedBan banEntry;
-            banEntry.subnet = (*it).first;
-            banEntry.banEntry = (*it).second;
+            banEntry.subnet = entry.first;
+            banEntry.banEntry = entry.second;
             cachedBanlist.append(banEntry);
         }