loader: add support for standard_validation layer enabled from env var

Also fix memory corruption issue with the original std_validation patch.
diff --git a/loader/loader.h b/loader/loader.h
index d40952e..800f774 100644
--- a/loader/loader.h
+++ b/loader/loader.h
@@ -489,9 +489,13 @@
     uint32_t expand_count,
     const char expand_names[][VK_MAX_EXTENSION_NAME_SIZE],
     uint32_t *layer_count, char ***ppp_layer_names);
-void loader_unexpand_dev_layer_names(uint32_t layer_count, char **layer_names,
+void loader_unexpand_dev_layer_names(const struct loader_instance *inst,
+                                     uint32_t layer_count, char **layer_names,
+                                     char **layer_ptr,
                                      const VkDeviceCreateInfo *pCreateInfo);
-void loader_unexpand_inst_layer_names(uint32_t layer_count, char **layer_names,
+void loader_unexpand_inst_layer_names(const struct loader_instance *inst,
+                                      uint32_t layer_count, char **layer_names,
+                                      char **layer_ptr,
                                       const VkInstanceCreateInfo *pCreateInfo);
 void loader_add_to_layer_list(const struct loader_instance *inst,
                               struct loader_layer_list *list,