Some memory allocation improvements

Some memory allocation improvements

 - All the memory-allocation macros now auto-check for failure and exit
   with a failure message that incudes the caller's file and lineno
   info.  This includes strdup().

 - Added the `--max-alloc=SIZE` option to be able to override the memory
   allocator's sanity-check limit.  It defaults to 1G (as before).
   Fixes bugzilla bug 12769.