blue gene: don'T register signal handlers

Instead of registering signal handlers, let the operating system
generate a core dump instead.

Suggested-by: Hal Finkel <hfinkel@anl.gov>
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
memory: call mallopt with default glibc values on Blue Gene/Q

Link: https://github.com/GeneAssembly/biosal/issues/819
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>