Revert "Fix memory leaks of special NAL sequences"

This reverts commit d9987105d0d9c27e920b4113875e82b315d050a4.
Revert "Fix the double-free bug and disable double free debugging."

This reverts commit 9bb395501172f754baacc1efe6f09af55627fa15.
Revert "Add double-free detection code to the pools"

This reverts commit 9cdcfd2522febcc2eb7f65d926a37cfa05f21323.
Revert "WIP optimization of object allocation and pools. There's currently a double free on the AvByteBufferDescriptor that I'm trying to track down."

This reverts commit 6600329580aace81321220d2e4000099ad27f4f7.
Remove pooling code due to higher concurrency latency that resulted in a net loss of performance.