Add 2013 to copyright.
Put all global variables in one global structure for readability.

Also rename some variables to avoid overlaps between global and
local names, again for readability.
Do not decompress concatenated zlib streams -- only gzip streams.
Make get_header() return values self-consistent.
Add zopfli deflate code.

Obtained using git clone https://code.google.com/p/zopfli/
Expose DeflatePart() in deflate.h interface.
Put decompression globals into a global structure for readability.

A previous commit titled "Put all global variables in one global
structure for readability" missed a bunch.  This fixes that.
Add option for compression level 11 to use zopfli.

This uses the zopfli code for deflation when -11 is specified.  It
is currently only implemented for parallel compression.  -11 will
not work with -p 1.  zopfli compresses a few percent better, at
the cost of one to two orders of magnitude increase in compression
time.
Add -11 option to documentation.
Fix handling of junk after compressed data.

This makes sure that gzip -cdf copies the junk to the output only
for gzip streams.  This correctly reports junk after gzip and zlib
streams.  This reports additional entries after the first entry in
a zip file.
pigz version 2.3