Modernize source code: last part (#6285)

* Modernize source code: last par

* Use empty when needed
* Use emplace_back instead of push_back when needed
* For range-based loops
* Initializers fixes
* constructors, destructors default
* c++ C stl includes

src/emerge.h

@@ -29,10 +29,10 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #define BLOCK_EMERGE_ALLOW_GEN   (1 << 0)
 #define BLOCK_EMERGE_FORCE_QUEUE (1 << 1)
 
-#define EMERGE_DBG_OUT(x) do {                         \
+#define EMERGE_DBG_OUT(x) {                            \
 	if (enable_mapgen_debug_info)                      \
 		infostream << "EmergeThread: " x << std::endl; \
-} while (0)
+}
 
 class EmergeThread;
 class INodeDefManager;