[libpng16] Suppress clang warnings about implicit sign changes in png.c

ANNOUNCE

@@ -43,6 +43,7 @@ Version 1.6.29beta03 [March 1, 2017]
   Avoid potential overflow of shift operations in png_do_expand() (Aaron Boxer).
   Change test ZLIB_VERNUM >= 0x1281 to ZLIB_VERNUM >= 0x1290 in pngrutil.c
     because Solaris 11 distributes zlib-1.2.8.f that is older than 1.2.8.1.
+  Suppress clang warnings about implicit sign changes in png.c
 
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CHANGES

@@ -5812,6 +5812,7 @@ Version 1.6.29beta03 [March 1, 2017]
   Avoid potential overflow of shift operations in png_do_expand() (Aaron Boxer).
   Change test ZLIB_VERNUM >= 0x1281 to ZLIB_VERNUM >= 0x1290 in pngrutil.c
     because Solaris 11 distributes zlib-1.2.8.f that is older than 1.2.8.1.
+  Suppress clang warnings about implicit sign changes in png.c
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit

png.c

 
 /* png.c - location for general purpose libpng functions
  *
- * Last changed in libpng 1.6.28 [January 5, 2017%]
+ * Last changed in libpng 1.6.29 [(PENDING RELEASE)]
  * Copyright (c) 1998-2002,2004,2006-2017 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -776,14 +776,14 @@ png_get_copyright(png_const_structrp png_ptr)
 #else
 #  ifdef __STDC__
    return PNG_STRING_NEWLINE \
-      "libpng version 1.6.29beta03 - February 22, 2017" PNG_STRING_NEWLINE \
+      "libpng version 1.6.29beta03 - March 1, 2017" PNG_STRING_NEWLINE \
       "Copyright (c) 1998-2002,2004,2006-2017 Glenn Randers-Pehrson" \
       PNG_STRING_NEWLINE \
       "Copyright (c) 1996-1997 Andreas Dilger" PNG_STRING_NEWLINE \
       "Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc." \
       PNG_STRING_NEWLINE;
 #  else
-   return "libpng version 1.6.29beta03 - February 22, 2017\
+   return "libpng version 1.6.29beta03 - March 1, 2017\
       Copyright (c) 1998-2002,2004,2006-2017 Glenn Randers-Pehrson\
       Copyright (c) 1996-1997 Andreas Dilger\
       Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.";
@@ -4260,13 +4260,13 @@ png_set_option(png_structrp png_ptr, int option, int onoff)
    if (png_ptr != NULL && option >= 0 && option < PNG_OPTION_NEXT &&
       (option & 1) == 0)
    {
-      png_uint_32 mask = 3 << option;
-      png_uint_32 setting = (2 + (onoff != 0)) << option;
+      png_uint_32 mask = 3U << option;
+      png_uint_32 setting = (2U + (onoff != 0)) << option;
       png_uint_32 current = png_ptr->options;
 
       png_ptr->options = (png_uint_32)(((current & ~mask) | setting) & 0xff);
 
-      return (current & mask) >> option;
+      return (int)(current & mask) >> option;
    }
 
    return PNG_OPTION_INVALID;