Move *priv members to the end of internal structures

This commit moves provider_priv and pool_priv members in internal
structures due to compatibility issues. From now, adding new ops
will not break accessing these members.

Author: KFilipek

src/memory_pool_internal.h

@@ -26,14 +26,16 @@ extern "C" {
 
 typedef struct umf_memory_pool_t {
     void *pool_priv;
-    umf_memory_pool_ops_t ops;
     umf_pool_create_flags_t flags;
 
     // Memory provider used by the pool.
     umf_memory_provider_handle_t provider;
 
     utils_mutex_t lock;
     void *tag;
+
+    // ops should be the last due to possible change size in the future
+    umf_memory_pool_ops_t ops;
 } umf_memory_pool_t;
 
 #ifdef __cplusplus

src/memory_provider_internal.h

@@ -21,8 +21,9 @@ extern "C" {
 #endif
 
 typedef struct umf_memory_provider_t {
-    umf_memory_provider_ops_t ops;
     void *provider_priv;
+    // ops should be the last due to possible change size in the future
+    umf_memory_provider_ops_t ops;
 } umf_memory_provider_t;
 
 void *umfMemoryProviderGetPriv(umf_memory_provider_handle_t hProvider);