That didn't work when cross-compiling.  Simply rely on limits.h.
If a compiler does not have limits.h, then zconf.h.in should be
modified to define Z_U4 as an unsiged four-byte integer type in
order for crc32() to be fast.

This also simplifies and makes more portable to check for a four-
byte type using limits.h.

The function is only available if stdarg.h is available.

 * Use -DASM686=1 to build with i686 asm.
 * Use -DAMD64=1 to build with amd64 asm.

Facilitate multi-platform compilation, e.g.:
nmake -f pathto\zlib\win32\Makefile.msc TOP=pathto\zlib

Mac OS X's linker (derived from LLVM, not GNU binutils) does not support
--version-script. Don't specify it on this platform.

Previously, spaces in ${CMAKE_CURRENT_SOURCE_PATH} would expand into
multiple linker arguments.

Also correct typo for 64-bit debug build.

Suggested by E. Timothy Uy.

inftrees.c compared the number of used table entries to the maximum
allowed value using >= instead of >.  This patch fixes those to use
>.  The bug was discovered by Ignat Kolesnichenko of Yandex LC
where they have run petabytes of data through zlib.  Triggering the
bug is apparently very rare, seeing as how it has been out there in
the wild for almost three years before being discovered.  The bug
is instantiated only if the exact maximum number of decoding table
entries, ENOUGH_DISTS or ENOUGH_LENS is used by the block being
decoded, resulting in the false positive of overflowing the table.

Without this fix, it would be possible to construct inputs to puff
that would cause it to segfault.

If the deflateInit2() called for the first gzwrite() failed with a
Z_MEM_ERROR, then a subsequent gzclose() would try to free an
already freed pointer.  This fixes that.

A gzopen() to write (mode "w") followed immediately by a gzclose()
would output an empty zero-length file.  What it should do is write
an empty gzip file, with the gzip header, empty deflate content,
and gzip trailer totalling 20 bytes.  This fixes it to do that.

Avoid the use of an uninitialized value when the write buffers have
not been initialized.  A recent change to avoid the use of strm->
next_in in order to resolve some const conflicts added the use of
state->in in its place.  This patch avoids the use of state->in
when it is not initialized.  Nothing bad would actually happen,
since two variables set to the same unintialized value are
subtracted.  However valgrind was rightly complaining.  So this
fixes that.

Also clean up comparisons between different types, and some odd
indentation problems that showed up somehow.

A new endless loop was introduced by the clang compiler, which
apparently does odd things when the right operand of << is equal to
or greater than the number of bits in the type.  The C standard in
fact states that the behavior of << is undefined in that case.  The
loop was rewritten to use single-bit shifts.

This patch allows zlib to compile cleanly with the -Wcast-qual gcc
warning enabled, but only if ZLIB_CONST is defined, which adds
const to next_in and msg in z_stream and in the in_func prototype.
A --const option is added to ./configure which adds -DZLIB_CONST
to the compile flags, and adds -Wcast-qual to the compile flags
when ZLIBGCCWARN is set in the environment.

There were two problems before that this fixes.  One was that the
check for the compiler error return code preceded the determination
of the compiler and its options.  The other was that the checks
for compiler and library characteristics could be fooled if the
error options were set to reject K&R-style C.  configure now aborts
if the compiler produces a hard error on K&R-style C.

In addition, aborts of configure are now consistent, and remove
any temporary files.