util: abort if we try to allocate more than a MB

util: abort if we try to allocate more than a MB

The ssize_t cast upsets coverity for some reason but we can be a lot more
restrictive here anyway. Quick analysis of the zalloc calls in the test suite
show the largest allocation is 9204 bytes.

Let's put a cap on for one MB, anything above that is likely some memory
corruption and should be caught early.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Matheus Santana <embs@cin.ufpe.br>