vpxenc: die on realloc failures

Identified as a possible cause of issue #308, the code was silently
ignoring realloc failures, which would lead to corruption, memory
leaks, and likely a crash. The best we can do in this case is die
gracefully.

Change-Id: Ie5f6a853d367015be5b9712bd742778f3baeefd9
1 file changed