MDEV-10814: Don't coredump query cache

merge fix: additional_data_size is a size_t class Query_cache member.

sql/sql_cache.cc

@@ -2594,7 +2594,7 @@ size_t Query_cache::init_cache()
 {
   size_t mem_bin_count, num, step;
   size_t mem_bin_size, prev_size, inc;
-  size_t additional_data_size, max_mem_bin_size, approx_additional_data_size;
+  size_t max_mem_bin_size, approx_additional_data_size;
   int align;
 
   DBUG_ENTER("Query_cache::init_cache");

sql/sql_cache.h

@@ -337,7 +337,7 @@ class Query_cache
     till the end of a flush operation.
   */
   mysql_mutex_t structure_guard_mutex;
-  ulong additional_data_size;
+  size_t additional_data_size;
   uchar *cache;					// cache memory
   Query_cache_block *first_block;		// physical location block list
   Query_cache_block *queries_blocks;		// query list (LIFO)