Sync zlib sources with GCC, upgrading to 1.2.10.

Changes in 1.2.10 (2 Jan 2017)
- Avoid warnings on snprintf() return value
- Fix bug in deflate_stored() for zero-length input
- Fix bug in gzwrite.c that produced corrupt gzip files
- Remove files to be installed before copying them in Makefile.in
- Add warnings when compiling with assembler code

Changes in 1.2.9 (31 Dec 2016)
- Fix contrib/minizip to permit unzipping with desktop API [Zouzou]
- Improve contrib/blast to return unused bytes
- Assure that gzoffset() is correct when appending
- Improve compress() and uncompress() to support large lengths
- Fix bug in test/example.c where error code not saved
- Remedy Coverity warning [Randers-Pehrson]
- Improve speed of gzprintf() in transparent mode
- Fix inflateInit2() bug when windowBits is 16 or 32
- Change DEBUG macro to ZLIB_DEBUG
- Avoid uninitialized access by gzclose_w()
- Allow building zlib outside of the source directory
- Fix bug that accepted invalid zlib header when windowBits is zero
- Fix gzseek() problem on MinGW due to buggy _lseeki64 there
- Loop on write() calls in gzwrite.c in case of non-blocking I/O
- Add --warn (-w) option to ./configure for more compiler warnings
- Reject a window size of 256 bytes if not using the zlib wrapper
- Fix bug when level 0 used with Z_HUFFMAN or Z_RLE
- Add --debug (-d) option to ./configure to define ZLIB_DEBUG
- Fix bugs in creating a very large gzip header
- Add uncompress2() function, which returns the input size used
- Assure that deflateParams() will not switch functions mid-block
- Dramatically speed up deflation for level 0 (storing)
- Add gzfread(), duplicating the interface of fread()
- Add gzfwrite(), duplicating the interface of fwrite()
- Add deflateGetDictionary() function
- Use snprintf() for later versions of Microsoft C
- Fix *Init macros to use z_ prefix when requested
- Replace as400 with os400 for OS/400 support [Monnerat]
- Add crc32_z() and adler32_z() functions with size_t lengths
- Update Visual Studio project files [AraHaan]

zlib/test/infcover.c

@@ -1,5 +1,5 @@
 /* infcover.c -- test zlib's inflate routines with full code coverage
- * Copyright (C) 2011 Mark Adler
+ * Copyright (C) 2011, 2016 Mark Adler
  * For conditions of distribution and use, see copyright notice in zlib.h
  */
 
@@ -237,14 +237,14 @@ local void mem_done(z_stream *strm, char *prefix)
 
 /* Decode a hexadecimal string, set *len to length, in[] to the bytes.  This
    decodes liberally, in that hex digits can be adjacent, in which case two in
-   a row writes a byte.  Or they can delimited by any non-hex character, where
-   the delimiters are ignored except when a single hex digit is followed by a
-   delimiter in which case that single digit writes a byte.  The returned
-   data is allocated and must eventually be freed.  NULL is returned if out of
-   memory.  If the length is not needed, then len can be NULL. */
+   a row writes a byte.  Or they can be delimited by any non-hex character,
+   where the delimiters are ignored except when a single hex digit is followed
+   by a delimiter, where that single digit writes a byte.  The returned data is
+   allocated and must eventually be freed.  NULL is returned if out of memory.
+   If the length is not needed, then len can be NULL. */
 local unsigned char *h2b(const char *hex, unsigned *len)
 {
-    unsigned char *in;
+    unsigned char *in, *re;
     unsigned next, val;
 
     in = malloc((strlen(hex) + 1) >> 1);
@@ -268,8 +268,8 @@ local unsigned char *h2b(const char *hex, unsigned *len)
     } while (*hex++);       /* go through the loop with the terminating null */
     if (len != NULL)
         *len = next;
-    in = reallocf(in, next);
-    return in;
+    re = realloc(in, next);
+    return re == NULL ? in : re;
 }
 
 /* generic inflate() run, where hex is the hexadecimal input data, what is the