libs/zlib: bump to latest stable release 1.2.12 (CVE-2018-25032)

libs/zlib: bump to latest stable release 1.2.12 (CVE-2018-25032)

List of changes since previous release from 2018 is quite long:

 * Fix crc32.c to compile local functions only if used.
 * Check for cc masquerading as gcc or clang in configure.
 * Remove destructive aspects of make distclean.
 * Separate out address sanitizing from warnings in configure.
 * Eliminate use of ULL constants.
 * Add fallthrough comments for gcc.
 * Clean up minizip to reduce warnings for testing.
 * Fix unztell64() in minizip to work past 4GB. (Daniël Hörchner)
 * minizip warning fix if MAXU32 already defined. (gvollant)
 * Replace black/white with allow/block. (theresa-m)
 * Fix indentation in minizip's zip.c.
 * Improve portability of contrib/minizip.
 * Correct typo in blast.c.
 * Change macro name in inflate.c to avoid collision in VxWorks.
 * Clarify gz* function interfaces, referring to parameter names.
 * Fix error in comment on the polynomial representation of a byte.
 * Fix memory leak on error in gzlog.c.
 * Avoid adding empty gzip member after gzflush with Z_FINISH.
 * Explicitly note that the 32-bit check values are 32 bits.
 * Use ARM crc32 instructions if the ARM architecture has them.
 * Add use of the ARMv8 crc32 instructions when requested.
 * Correct comment in crc32.c.
 * Don't bother computing check value after successful inflateSync().
 * Use atomic test and set, if available, for dynamic CRC tables.
 * Speed up software CRC-32 computation by a factor of 1.5 to 3.
 * Add crc32_combine_gen() and crc32_combine_op() for fast combines.
 * Add tables for crc32_combine(), to speed it up by a factor of 200.
 * Fix the zran.c example to work on a multiple-member gzip file.
 * Add gznorm.c example, which normalizes gzip files.
 * Show all the codes for the maximum tables size in enough.c.
 * Clarify that prefix codes are counted in enough.c.
 * Use inline function instead of macro for index in enough.c.
 * Clean up code style in enough.c, update version.
 * Use a macro for the printf format of big_t in enough.c.
 * Use a structure to make globals in enough.c evident.
 * Assure that the number of bits for deflatePrime() is valid.
 * Fix a bug that can crash deflate on some input when using Z_FIXED.
 * Correct the initialization requirements for deflateInit2().
 * Emphasize the need to continue decompressing gzip members.
 * Add legal disclaimer to README.
 * Fix deflateEnd() to not report an error at start of raw deflate.
 * Remove old assembler code in which bugs have manifested.
 * Make the names in functions declarations identical to definitions.
 * Avoid an undefined behavior of memcpy() in _tr_stored_block().
 * Avoid undefined behaviors of memcpy() in gz*printf().
 * Avoid an undefined behavior of memcpy() in gzappend().
 * Avoid the use of ptrdiff_t.
 * Handle case where inflateSync used when header never processed.
 * Don't compute check value for raw inflate if asked to validate.
 * Add address checking in clang to -w option of configure.
 * Return an error if the gzputs string length can't fit in an int.
 * Small speedup to inflate [psumbera].
 * Update use of errno for newer Windows CE versions.
 * Avoid some conversion warnings in gzread.c and gzwrite.c.
 * Have Makefile return non-zero error code on test failure.
 * Avoid a conversion error in gzseek when off_t type too small.
 * Fix CLEAR_HASH macro to be usable as a single statement.
 * Fix bug when window full in deflate_stored().
 * Limit hash table inserts after switch from stored deflate.
 * Permit a deflateParams() parameter change as soon as possible.
 * Cygwin does not have _wopen(), so do not create gzopen_w() there.

Removed 006-fix-compressor-crash-on-certain-inputs.patch which was
hotfix for CVE-2018-25032 and is now included in this release.

This release is not available on @SF (yet?) so the sources are now
pulled from GitHub.

Fixes: CVE-2018-25032
Signed-off-by: Petr Štetiar <ynezz@true.cz>