Bug#11766249 bug#59316: PARTITIONING AND INDEX_MERGE MEMORY LEAK

When executing row-ordered-retrieval index merge,
the handler was cloned, but it used the wrong
memory root, so instead of allocating memory
on the thread/query's mem_root, it used the table's
mem_root, resulting in non released memory in the
table object, and was not freed until the table was
closed.

Solution was to ensure that memory used during cloning
of a handler was allocated from the correct memory root.

This was implemented by fixing handler::clone() to also
take a name argument, so it can be used with partitioning.
And in ha_partition only allocate the ha_partition's ref, and
call the original ha_partition partitions clone() and set at cloned
partitions.

Fix of .bzrignore on Windows with VS 2010

sql/handler.h

@@ -1166,7 +1166,7 @@ public:
     DBUG_ASSERT(locked == FALSE);
     /* TODO: DBUG_ASSERT(inited == NONE); */
   }
-  virtual handler *clone(MEM_ROOT *mem_root);
+  virtual handler *clone(const char *name, MEM_ROOT *mem_root);
   /** This is called after create to allow us to set up cached variables */
   void init()
   {