[Issue 22998] New: Update to zlib 1.2.12

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=22998

          Issue ID: 22998
           Summary: Update to zlib 1.2.12
           Product: D
           Version: D2
          Hardware: x86
                OS: Windows
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: phobos
          Assignee: nobody at puremagic.com
          Reporter: bcallah at openbsd.org

Hello --

I've updated the copy of zlib in Phobos.

Here's a reprinting of the big-ticket items from the zlib.net homepage:
Version 1.2.12 has these key improvements over 1.2.11:

* Fix a deflate bug when using the Z_FIXED strategy that can result in
out-of-bound accesses.
* Fix a deflate bug when the window is full in deflate_stored().
* Speed up CRC-32 computations by a factor of 1.5 to 3.
* Use the hardware CRC-32 instruction on ARMv8 processors.
* Speed up crc32_combine() with powers of x tables.
* Add crc32_combine_gen() and crc32_combine_op() for fast combines.
Due to the bug fixes, any installations of 1.2.11 should be replaced with
1.2.12.

Also maintains the fix from here:
https://github.com/ibara/phobos/commit/1b6cf80232f19e581f72869a4b339580416dd72d

Everything appears OK on my OpenBSD/amd64 machine. But perhaps more testing
from others is in order.

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