Bug #38187: Error 153 when creating savepoints

Detailed revision comments:

r3911 | sunny | 2009-01-13 14:15:24 +0200 (Tue, 13 Jan 2009) | 13 lines
branches/5.1: Fix Bug#38187 Error 153 when creating savepoints
InnoDB previously treated savepoints as a stack e.g.,
  SAVEPOINT a;
  SAVEPOINT b;
  SAVEPOINT c;
  SAVEPOINT b; <- This would delete b and c.

This fix changes the behavior to:
  SAVEPOINT a;
  SAVEPOINT b;
  SAVEPOINT c;
  SAVEPOINT b; <- Does not delete savepoint c