fix implicit declaration of function 'GetCurrentThread' and related warnings

Codec/entropy_threading.c

@@ -327,7 +327,7 @@ THREAD_PROC(EntropyWorkerThreadProc, lpParam)
 		HANDLE hCurrentThread = GetCurrentThread();
 		SetThreadAffinityMask(hCurrentThread, decoder->thread_cntrl.affinity);
 #else
-		pthread_t thread = GetCurrentThread();
+		pthread_t thread = pthread_self();
 		uint32_t thread_affinity = decoder->thread_cntrl.affinity;
 		SetThreadAffinityMask(thread, &thread_affinity);
 #endif
@@ -403,7 +403,7 @@ THREAD_PROC(ParallelThreadProc, lpParam)
 		HANDLE hCurrentThread = GetCurrentThread();
 		SetThreadAffinityMask(hCurrentThread,decoder->thread_cntrl.affinity);
 #else
-		pthread_t thread = GetCurrentThread();
+		pthread_t thread = pthread_self();
 		uint32_t thread_affinity = decoder->thread_cntrl.affinity;
 		SetThreadAffinityMask(thread, &thread_affinity);
 #endif

Codec/thread.c

@@ -23,13 +23,7 @@
 
 #include "thread.h"
 
-#ifdef _WINDOWS
-#else
-
-pthread_t GetCurrentThread(void)
-{
-	return pthread_self();
-}
+#ifndef _WINDOWS
 
 //TODO: How to set the thread affinity on Macintosh and Linux?
 void SetThreadAffinityMask(pthread_t thread, uint32_t *thread_affinity_mask)