Fix lua_yield() from C hook.

Reported by Jason Carr.

src/lj_api.c

@@ -1210,11 +1210,12 @@ LUA_API int lua_yield(lua_State *L, int nresults)
       setcont(top, lj_cont_hook);
       if (LJ_FR2) top++;
       setframe_pc(top, cframe_pc(cf)-1);
-      if (LJ_FR2) top++;
+      top++;
       setframe_gc(top, obj2gco(L), LJ_TTHREAD);
+      if (LJ_FR2) top++;
       setframe_ftsz(top, ((char *)(top+1)-(char *)L->base)+FRAME_CONT);
       L->top = L->base = top+1;
-#if LJ_TARGET_X64
+#if ((defined(__GNUC__) || defined(__clang__)) && (LJ_TARGET_X64 || defined(LUAJIT_UNWIND_EXTERNAL)) && !LJ_NO_UNWIND) || LJ_TARGET_WINDOWS
       lj_err_throw(L, LUA_YIELD);
 #else
       L->cframe = NULL;