headers: Fix mingw-w64-libraries/winpthreads/src/thread.h

Move WINPTHREAD_API left to return type of __pth_gpointer_locked so
cl.exe does not choke with C2059 (syntax error).

Signed-off-by: Kirill Makurin <maiddaisuki@outlook.com>
Signed-off-by: LIU Hao <lh_mouse@126.com>
1 file changed