Trim fat from misc_language.h and refactor net_peerlist.h

The following were removed from misc_language.h:
* Includes to `<limit>` and `<functional>`
* Macros `STD_TRY_BEGIN` and `STD_TRY_CATCH`
* Function `get_max_t_val`
* Iterator-related functions `move_it_forward` and `move_it_backward`
* struct `less_as_pod`
* memory compare function `is_less_as_pod`

All the above were unmentioned throughout the rest of the project except for `move_it_backward`,
which was mentioned 3 times in `net_peerlist.h`. However, the same exact behaviour can be
acheived with `std::advance()`, so I unloaded the iterator logic into a private static inline
method `peerlist_manager::get_nth_latest_peer()`. Personally, I think this has the side effect
of making the functions `get_white_peer_by_index()`, `get_gray_peer_by_index()`, and
`get_random_gray_peer()` clearer in their implementation.

contrib/epee/include/misc_language.h

@@ -30,74 +30,14 @@
 
 #include <boost/utility/value_init.hpp>
 #include <boost/shared_ptr.hpp>
-#include <limits>
-#include <functional>
 #include <vector>
 namespace epee
 {
-#define STD_TRY_BEGIN() try {
-
-#define STD_TRY_CATCH(where_, ret_val) \
-	} \
-	catch (const std::exception  &e) \
-	{ \
-		LOG_ERROR("EXCEPTION: " << where_  << ", mes: "<< e.what());  \
-		return ret_val; \
-	} \
-	catch (...) \
-	{ \
-		LOG_ERROR("EXCEPTION: " << where_ ); \
-		return ret_val; \
-	}
-
-
-
 #define AUTO_VAL_INIT(v)   boost::value_initialized<decltype(v)>()
 
 namespace misc_utils
 {
-	template<typename t_type>
-		t_type get_max_t_val(t_type t)
-		{
-			return (std::numeric_limits<t_type>::max)();
-		}
-
-		
-	template<typename t_iterator>
-		t_iterator move_it_forward(t_iterator it, size_t count)
-		{
-			while(count--)
-				it++;
-			return it;
-		}
-
-    template<typename t_iterator>
-    t_iterator move_it_backward(t_iterator it, size_t count)
-    {
-      while(count--)
-        it--;
-      return it;
-    }
-
-
-	// TEMPLATE STRUCT less
-	template<class _Ty>
-	struct less_as_pod
-		: public std::binary_function<_Ty, _Ty, bool>
-	{	// functor for operator<
-		bool operator()(const _Ty& _Left, const _Ty& _Right) const
-		{	// apply operator< to operands
-			return memcmp(&_Left, &_Right, sizeof(_Left)) < 0;
-		}
-	};
-
-  template<class _Ty>
-  bool is_less_as_pod(const _Ty& _Left, const _Ty& _Right)
-  {	// apply operator< to operands
-      return memcmp(&_Left, &_Right, sizeof(_Left)) < 0;
-  }
-	
-	bool sleep_no_w(long ms );
+  bool sleep_no_w(long ms);
 
   template <typename T>
   T get_mid(const T &a, const T &b)

src/p2p/net_peerlist.h

@@ -31,6 +31,7 @@
 #pragma once
 
 #include <iosfwd>
+#include <iterator>
 #include <list>
 #include <string>
 #include <vector>
@@ -184,6 +185,7 @@ namespace nodetool
   private: 
     void trim_white_peerlist();
     void trim_gray_peerlist();
+    static peerlist_entry get_nth_latest_peer(peers_indexed& peerlist, size_t n);
 
     friend class boost::serialization::access;
     epee::critical_section m_peerlist_lock;
@@ -214,6 +216,16 @@ namespace nodetool
     }
   }
   //--------------------------------------------------------------------------------------------------
+  inline
+  peerlist_entry peerlist_manager::get_nth_latest_peer(peers_indexed& peerlist, const size_t n)
+  {
+    // Is not thread-safe nor does it check bounds. Do this before calling. Indexing starts at 0.
+    peers_indexed::index<by_time>::type& by_time_index = peerlist.get<by_time>();
+    auto by_time_it = --by_time_index.end();
+    std::advance(by_time_it, -((long long) n));
+    return *by_time_it;
+  }
+  //--------------------------------------------------------------------------------------------------
   inline 
   bool peerlist_manager::merge_peerlist(const std::vector<peerlist_entry>& outer_bs, const std::function<bool(const peerlist_entry&)> &f)
   {
@@ -235,8 +247,7 @@ namespace nodetool
     if(i >= m_peers_white.size())
       return false;
 
-    peers_indexed::index<by_time>::type& by_time_index = m_peers_white.get<by_time>();
-    p = *epee::misc_utils::move_it_backward(--by_time_index.end(), i);    
+    p = peerlist_manager::get_nth_latest_peer(m_peers_white, i);
     return true;
   }
   //--------------------------------------------------------------------------------------------------
@@ -247,8 +258,7 @@ namespace nodetool
     if(i >= m_peers_gray.size())
       return false;
 
-    peers_indexed::index<by_time>::type& by_time_index = m_peers_gray.get<by_time>();
-    p = *epee::misc_utils::move_it_backward(--by_time_index.end(), i);    
+    p = peerlist_manager::get_nth_latest_peer(m_peers_gray, i);
     return true;
   }
   //--------------------------------------------------------------------------------------------------
@@ -437,9 +447,7 @@ namespace nodetool
     }
 
     size_t random_index = crypto::rand_idx(m_peers_gray.size());
-
-    peers_indexed::index<by_time>::type& by_time_index = m_peers_gray.get<by_time>();
-    pe = *epee::misc_utils::move_it_backward(--by_time_index.end(), random_index);
+    pe = peerlist_manager::get_nth_latest_peer(m_peers_gray, random_index);
 
     return true;