Fixed TLS build on Windows GCC/MVSC

Cleanup TLS compile

src/Mem_win.cpp

@@ -153,7 +153,7 @@ bool Mem::allocate(const Options* options)
     m_memorySize = 0;
 
     size_t scratchPadSize = m_algo == Options::ALGO_CRYPTONIGHT ? MEMORY : MEMORY_LITE;
-    for (int i=0; i < m_threads; i++) {
+    for (size_t i=0; i < m_threads; i++) {
         m_memorySize += sizeof(cryptonight_ctx);
         m_memorySize += scratchPadSize * getThreadHashFactor(i);
     }