BUG#36639: subselect.test crashes on 64 bit pentium4 when compiled for valgrind, commit into 5.0

- Use the compiler's default copy constructor for QUICK_RANGE_SELECT. 
  bcopy(this, copy, ...) call caused some odd action on gcc-4.1.2 on x86_64

sql/opt_range.cc

@@ -7103,6 +7103,13 @@ QUICK_SELECT_DESC::QUICK_SELECT_DESC(QUICK_RANGE_SELECT *q,
   used_key_parts (used_key_parts_arg)
 {
   QUICK_RANGE *r;
+  /* 
+    Use default MRR implementation for reverse scans. No table engine
+    currently can do an MRR scan with output in reverse index order.
+  */
+  multi_range_length= 0;
+  multi_range= NULL;
+  multi_range_buff= NULL;
 
   QUICK_RANGE **pr= (QUICK_RANGE**)ranges.buffer;
   QUICK_RANGE **end_range= pr + ranges.elements;

sql/opt_range.h

@@ -329,14 +329,7 @@ public:
   void dbug_dump(int indent, bool verbose);
 #endif
 private:
-  /* Used only by QUICK_SELECT_DESC */
-  QUICK_RANGE_SELECT(const QUICK_RANGE_SELECT& org) : QUICK_SELECT_I()
-  {
-    bcopy(&org, this, sizeof(*this));
-    multi_range_length= 0;
-    multi_range= NULL;
-    multi_range_buff= NULL;
-  }
+  /* Default copy ctor used by QUICK_SELECT_DESC */
 };