Fix VC++ 2015 64-bit truncation warning in zlib

third_party/zlib/google.patch

+diff -ru zlib-1.2.5/crc_folding.c zlib/crc_folding.c
+--- zlib-1.2.5/crc_folding.c
++++ zlib/crc_folding.c
+@@ -283,7 +283,9 @@
+         goto partial;
+     }
+
+-    algn_diff = 0 - (unsigned long)src & 0xF;
++    // Double cast to avoid truncation errors in 64-bit builds by making the
++    // truncation explicit.
++    algn_diff = 0 - (unsigned long)(size_t)src & 0xF;
+     if (algn_diff) {
+         xmm_crc_part = _mm_loadu_si128((__m128i *)src);
+         _mm_storeu_si128((__m128i *)dst, xmm_crc_part);
 diff -ru zlib-1.2.5/gzlib.c zlib/gzlib.c
 --- zlib-1.2.5/gzlib.c
 +++ zlib/gzlib.c
 @@ -5,7 +5,9 @@
  
  #include "gzguts.h"
  
 -#if defined(_LARGEFILE64_SOURCE) && _LFS64_LARGEFILE-0
 +#if defined(_WIN32)
 +#  define LSEEK (z_off64_t)_lseeki64
@@ skipping 220 matching lines @@
 +#  ifdef adler32_combine
 +#    undef adler32_combine
 +#  endif
  #  define adler32_combine adler32_combine64
 +#  ifdef crc32_combine
 +#    undef crc32_combine
 +#  endif
  #  define crc32_combine crc32_combine64
  #  ifdef _LARGEFILE64_SOURCE
       ZEXTERN gzFile ZEXPORT gzopen64 OF((const char *, const char *));