Rename thread source files

This to reflect that they now contain more than TLS.

src/wl_platform.h

diff --git a/src/wl_platform.h b/src/wl_platform.h
index 6206985..c543d82 100644
--- a/src/wl_platform.h
+++ b/src/wl_platform.h
@@ -43,7 +43,7 @@
 typedef VkResult (APIENTRY *PFN_vkCreateWaylandSurfaceKHR)(VkInstance,const VkWaylandSurfaceCreateInfoKHR*,const VkAllocationCallbacks*,VkSurfaceKHR*);
 typedef VkBool32 (APIENTRY *PFN_vkGetPhysicalDeviceWaylandPresentationSupportKHR)(VkPhysicalDevice,uint32_t,struct wl_display*);
 
-#include "posix_tls.h"
+#include "posix_thread.h"
 #include "posix_time.h"
 #include "linux_joystick.h"
 #include "xkb_unicode.h"