windows/SDL_systhread.c: remove some dead code.

src/thread/windows/SDL_systhread.c

@@ -30,47 +30,18 @@
 #include "../SDL_systhread.h"
 #include "SDL_systhread_c.h"
 
-#ifndef SDL_PASSED_BEGINTHREAD_ENDTHREAD
-/* We'll use the C library from this DLL */
-#include <process.h>
-
 #ifndef STACK_SIZE_PARAM_IS_A_RESERVATION
 #define STACK_SIZE_PARAM_IS_A_RESERVATION 0x00010000
 #endif
 
-/* Cygwin gcc-3 ... MingW64 (even with a i386 host) does this like MSVC. */
-#if (defined(__MINGW32__) && (__GNUC__ < 4))
-typedef unsigned long(__cdecl *pfnSDL_CurrentBeginThread)(void *, unsigned,
-                                                          unsigned(__stdcall *func)(void *), void *arg,
-                                                          unsigned, unsigned *threadID);
-typedef void(__cdecl *pfnSDL_CurrentEndThread)(unsigned code);
-
-#elif defined(__WATCOMC__)
-/* This is for Watcom targets except OS2 */
-#if __WATCOMC__ < 1240
-#define __watcall
-#endif
-typedef unsigned long (__watcall * pfnSDL_CurrentBeginThread) (void *,
-                                                               unsigned,
-                                                               unsigned
-                                                               (__stdcall *
-                                                                func) (void
-                                                                       *),
-                                                               void *arg,
-                                                               unsigned,
-                                                               unsigned
-                                                               *threadID);
-typedef void (__watcall * pfnSDL_CurrentEndThread) (unsigned code);
-
-#else
+#ifndef SDL_PASSED_BEGINTHREAD_ENDTHREAD
+/* We'll use the C library from this DLL */
+#include <process.h>
 typedef uintptr_t(__cdecl *pfnSDL_CurrentBeginThread)(void *, unsigned,
-                                                      unsigned(__stdcall *
-                                                                   func)(void
-                                                                             *),
+                                                      unsigned(__stdcall *func)(void*),
                                                       void *arg, unsigned,
                                                       unsigned *threadID);
 typedef void(__cdecl *pfnSDL_CurrentEndThread)(unsigned code);
-#endif
 #endif /* !SDL_PASSED_BEGINTHREAD_ENDTHREAD */
 
 static DWORD RunThread(void *data)