ORDER BY could cause a server crash

Dependent subqueries like

  SELECT COUNT(*) FROM t1, t2 WHERE t2.b
   IN (SELECT DISTINCT t2.b FROM t2 WHERE t2.b = t1.a)

caused a memory leak proportional to the
number of outer rows.


The make_simple_join() function has been modified to
JOIN class method to store join_tab_reexec and
table_reexec values in the parent join only
(make_simple_join of tmp_join may access these values
via 'this' pointer of the parent JOIN).

NOTE: this patch doesn't include standard test case (this is
"out of memory" bug). See bug #42037 page for test cases.


sql/sql_select.cc:
  Bug #42037: Queries containing a subquery with DISTINCT and
              ORDER BY could cause a server crash
  
  The make_simple_join() function has been modified to
  JOIN class method to store join_tab_reexec and
  table_reexec values in the parent join only.
sql/sql_select.h:
  Bug #42037: Queries containing a subquery with DISTINCT and
              ORDER BY could cause a server crash
  
  1. The make_simple_join() function has been modified to
     JOIN class method.
  
  2. Type of JOIN::table_reexec field has been changed from
     TABLE** to TABLE *table_reexec[1]: this field always was
     NULL or a pointer to one-element array of pointers, so
     a pointer to a pointer has been replaced with one pointer
     and unnecessary memory allocation has been eliminated.