collie: replace malloc with xmalloc

This patch replaces malloc with xmalloc for simplicity.
It also catches SIGABRT to exit with EXIT_SYSFAIL in
the case of out of memory.

Signed-off-by: Harry Wei <harryxiyou@gmail.com>
Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>