Use after free check for all private zones too

[Gumpula, Suresh]

Hi ,
     Currently use after free check is available for  power of 2 malloc zones ( mt_rash_ctor/ m_trash_dotr ) which writes uma_junk(0xdeadc0de) on freed memory and
validates on reusing the object for others .
   Similary we( NETAPP)  have added a check for all  other private zones too with  trash_ctor/ trash_dtor .    We pass the trash_ctor/trash_dtor to uma_zcreate(9) if  it is called with NULL for constructor/destructor.
This change uncovered the couple of bugs inernally.  One  of this is in tcp timer bug
https://svnweb.freebsd.org/base?view=revision&revision=281599

Its a useful check and uncovers use after free bugs .  Would like to push this change .  Any comments/suggestions  please ?

Thanks
Suresh