Replace all assert(false) and assert(0) with abort()

Because assert() statements are not executed with a release/production
build, assert(false) and assert(0) statements are ignored and the
program's execution continues in an unexpected state. This could lead to
very weird and hard-to-debug situations, and potentially to corrupted
output traces.

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>