Faster bz2/lzma/zlib via new output buffering.
Also adds .readall() function to _compression.DecompressReader class
to take best advantage of this in the consume-all-output at once scenario.
Often a 5-20% speedup in common scenarios due to less data copying.
Contributed by Ma Lin.
GzipFile, BZ2File or LZMAFile. This defeats denial of service attacks
using compressed bombs (i.e. compressed payloads which decompress to a huge
size).
Patch by Martin Panter and Nikolaus Rath.