Support SV-COMP ReachSafety-Heap with BMC

[hajduakos]

This might be tricky, but Gazer does have some sort of memory models

[AdamZsofi]

Not top priority right now, but I'll run some benchmarks for this later, as we didn't even try this category earlier.

[sallaigy]

All of these programs seem to require malloc support, something we do not yet have in our flat memory model. I opened a separate ticket #86 to track that issue.