dynamically the new zlib as an alternative to the current zip functions.


To activate the new zlib it is enough to set Root.ZipMode = 1
in the system.rootrc file.
When setting Root.ZipMode to 1 (or 0) it is possible to read files
written with the old zip function.
Files written with Root.ZipMode=1 can only be read by versions
of Root >= 4.02/00.

A new function R__SetZipMode has been added in zip/Bits.h.
This function is called by TROOT::InitSystem with the value specified
in system.rootrc.

Some performance tests (on a P4 2.4GHz) show that
the new zlib version is as fast as the current ROOT zip functions when
writing and up to 10 per cent faster when reading.
                          oldzlib            newzlib
Event 1000 1 0   1         11.59s             11.46s
Event 1000 1 0  20          3.83s              3.31s
Event 1000 1 99  1         10.44s             10.98s
Event 1000 1 99 20          3.57s              3.17s
stress -b 30               13.01s             12.35s
stress -b 1000             61.67s             58.38s
bench                     151.99s            151.56s
stressLinear               35.87s             35.77s


git-svn-id: http://root.cern.ch/svn/root/trunk@10737 27541ba8-7e3a-0410-8455-c3a389f83636