Fix some leaks and constrain memory usage during decompression

[rib]

trafficstars

Unpacking large Xcode archives was leading to pbzx being OOM killed by the kernel.

Also adds some fflush() calls just so error messages aren't lost if pbzx crashes.

[matteyeux]

This is a mirror of Jonathan Levin tools, can you please contact him on Twitter or Newosxbook forum to report these bugs. Thank you.