libphobos: Don't call __gthread_key_delete in the emutls destroy function.

Fixes a EXC_BAD_ACCESS issue seen on Darwin when the libphobos DSO gets
unloaded.  Based on reading libgcc's emutls implementation, as it
doesn't call __gthread_key_delete directly, neither should libphobos.

libphobos/ChangeLog:

	* libdruntime/gcc/emutls.d (emutlsDestroyThread): Don't remove entry
	from global array.
	(_d_emutls_destroy): Don't call __gthread_key_delete.

libphobos/libdruntime/gcc/emutls.d

@@ -229,9 +229,6 @@ void** emutlsAlloc(shared __emutls_object* obj) nothrow @nogc
 extern (C) void emutlsDestroyThread(void* ptr) nothrow @nogc
 {
     auto arr = cast(TlsArray*) ptr;
-    emutlsMutex.lock_nothrow();
-    emutlsArrays.remove(arr);
-    emutlsMutex.unlock_nothrow();
 
     foreach (entry; *arr)
     {
@@ -308,9 +305,6 @@ void _d_emutls_scan(scope void delegate(void* pbeg, void* pend) nothrow cb) noth
 // Call this after druntime has been unloaded
 void _d_emutls_destroy() nothrow @nogc
 {
-    if (__gthread_key_delete(emutlsKey) != 0)
-        abort();
-
     (cast(Mutex) _emutlsMutex.ptr).__dtor();
     destroy(emutlsArrays);
 }