few changes to fix for XMALLOC_DEBUG:

 few changes to fix for XMALLOC_DEBUG:
 - check_free shouldn't be called with a NULL pointer
 - I needed to increase DBG_ARRY_SZ to handle larger alloc count
   (perhaps should we use realloc here to grow dynamically?)
 - cf_gen.c used inconsitently alloc funcs: xcalloc() but free(),
   resulting in check_free() to assert during make using cf_gen

Submitted by: Andres Kroomnaa <andre@online.ee>