Fulltext boolean mode phrase search may crash server on platforms
where size of pointer is not equal to size of unsigned integer
(in other words some 64-bit platforms).

The problem was integer overflow.

Affects 4.1 only.


myisam/ft_boolean_search.c:
  my_match_t::beg is unsigned int, that means type of expression
  (m[0].beg - 1) has unsigned type too. It may happen that instr()
  finds substring in the beggining of passed string, returning
  m[0].beg equal to 0. In this case value of expression (m[0].beg - 1)
  is equal to MAX_UINT.
  
  This is not a problem on platforms where sizeof(pointer) equals to
  sizeof(uint). That means ptr[(uint)-1] = ptr[(uint)MAX_UINT] = ptr - 1.
  
  On some 64-bit platforms where sizeof(pointer) is 8 and sizeof(uint)
  is 4, wrong address gets accessed. In other words ptr[(uint)-1] is
  equal to ptr + MAX_UINT.
mysql-test/r/fulltext.result:
  A test case for BUG#11392.
mysql-test/t/fulltext.test:
  A test case for BUG#11392.