Fix LP Bug#686184 - merge_debug test fails.

The reason for failure is that DBUG_EXECUTE_IF in mi_open()
only worked for Unix-formatted file names, due to strstr(name, "/crashed")

The fix change strstr() above to strstr(name, "crashed"), to it can work with 
Windows file names as well.

storage/myisam/mi_open.c

@@ -119,7 +119,7 @@ MI_INFO *mi_open(const char *name, int mode, uint open_flags)
                                                  dflt_key_cache);
 
     DBUG_EXECUTE_IF("myisam_pretend_crashed_table_on_open",
-                    if (strstr(name, "/crashed"))
+                    if (strstr(name, "crashed"))
                     {
                       my_errno= HA_ERR_CRASHED;
                       goto err;