Remove HAVE_PTHREAD_H config macro

Since we don't want to probe for winpthreads anymore, this macro isn't
usefull anymore

meson.build

@@ -37,9 +37,6 @@ if not meson.is_cross_build()
 else
     thread_dependency = cc.find_library('pthread', required: false)
 endif
-if thread_dependency.found()
-    cdata.set('HAVE_PTHREAD_H', 1)
-endif
 
 dav1d_inc_dirs = include_directories(['include', 'include/dav1d'])
 

src/thread.h

@@ -28,7 +28,7 @@
 #ifndef __DAV1D_THREAD_H__
 # define __DAV1D_THREAD_H__
 
-#if defined(_WIN32) && !defined(HAVE_PTHREAD_H)
+#if defined(_WIN32)
 
 #include <windows.h>
 

src/win32/thread.c

@@ -27,7 +27,7 @@
 
 #include "config.h"
 
-#if defined(_WIN32) && !defined(HAVE_PTHREAD_H)
+#if defined(_WIN32)
 
 #include <windows.h>
 #include <process.h>