Fixed valgrind complaints. This fixes the memory leak problems for
  procedured, and partially for functions. There's still a leak involving
  results from functions that turned out to be too involved, so it will be
  fixed separately.


mysql-test/r/sp.result:
  Fixed some minor mistake (spotted while debugging).
mysql-test/t/sp.test:
  Fixed some minor mistake (spotted while debugging).
sql/item_func.cc:
  Moved Item_func_sp::cleanup() from item_func.h to ease debugging,
  and made a debug output come out right.
sql/item_func.h:
  Moved Item_func_sp::cleanup() to item_func.cc to ease debugging.
sql/sp_head.cc:
  Fixed valgrind problems with the previous memory leak fix (unit cleanup and
  putting result field in a differen mem_root), and removed prealloc flag from
  init_alloc_root() calls.
sql/sp_rcontext.cc:
  New mem_root pointer used for return fields from functions.
sql/sp_rcontext.h:
  New mem_root pointer used for return fields from functions.