Capturing by value in the thread

[Kadir Erdem Demir]

It seems [=] functionality C++ does not exist in D.
By using a helper function I made that example work.

```d

import std.stdio;

auto localFoo(int x) {
     return (){ return x;};
}

void main() {
     int x = 10;

     auto lambda = (int capturedX = x) {
         writeln("Captured reference : ", capturedX);
     };

     auto localFoo = localFoo(x);

     x = 20;
     writeln(localFoo());// Outputs: Captured value: 10 --> That 
is what I need
     lambda();     // Outputs: 20

}

```	

But when I trying the same technique on std.Thread it does not 
work. Always reference is being captured.

```d


void InitCurrencies()
     {
         auto captureFuction(int index)
         {
             return (){
                 auto localIndex = index;
                 string[] currentChunk = 
ChunkedExchangePairNames(localIndex);
                 writeln("Thread index: ", localIndex, " pairs:
  ", currentChunk.join(";"));
                 foreach (exchangeName; currentChunk)
                     Connect(exchangeName, WebSocketType.All);
                 WebSocket.eventLoop(localLoopExited);
             };
         }

         for(int i = 0; i < m_ThreadCount; i++)
         {
             auto work = captureFuction(i);
             auto worker = new Thread({
                 work();
             });
             m_workerList ~= worker;
         }

         foreach(worker; m_workerList)
         {
             worker.start();
         }
     }

```	
writeln("Thread index: ", localIndex, " pairs: ", 
currentChunk.join(";"))
Always prints the last value of my for loop.


Is there a way to capture the value on anonymous function which 
is being passed t std.Thread