update zlib to 1.2.8

[Matthias Klose]

On 23.11.2015 19:13, Joel Brobecker wrote:
>> In GCC zlib is only used for libjava; for binutils and gdb it is used when
>> building without --with-system-zlib.  This just updates zlib from 1.2.7 to
>> 1.2.8 (released in 2013).  Applies cleanly, libjava still builds and doesn't
>> show any regressions in the testsuite.  Ok to apply (even if we already are
>> in stage3)?
>
>> +2015-11-23  Matthias Klose  <doko@ubuntu.com>
>> +
>> +       * Imported zlib 1.2.8; merged local changes.
>
> Should not be a problem for GDB, since we're not near branching time.
>
> Out of curiosity, what prompted this update? Just to be in sync with
> the latest? Or was there an actual bug that you hit which 1.2.8 fixes?

No, just a packaging issue with somebody mentioning a static binutils build. 
That's when I saw the outdated version.

Now updated in the GCC VCS.

Matthias