malloc should never fail, and if it does it is unlikely
that anything else useful can be done. Best approach is to
abort and let some super-daemon restart.
So define xmalloc, xcalloc, xrealloc, xstrdup which don't
fail but just print a message and exit. Then use those
removing all the tests for failure.
Also replace all "malloc;memset" sequences with 'xcalloc'.
Signed-off-by: NeilBrown <neilb@suse.de>