[libpng16] Disallow storing sRGB information when the sRGB is not supported.

Reverted previous attempt to allow gAMA and sRGB non-support with the
simplified API.
diff --git a/png.c b/png.c
index a894ac5..330fc2b 100644
--- a/png.c
+++ b/png.c
@@ -768,13 +768,13 @@
 #else
 #  ifdef __STDC__
    return PNG_STRING_NEWLINE \
-     "libpng version 1.6.2beta02 - April 14, 2013" PNG_STRING_NEWLINE \
+     "libpng version 1.6.2beta02 - April 18, 2013" PNG_STRING_NEWLINE \
      "Copyright (c) 1998-2013 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 1.6.2beta02 - April 14, 2013\
+      return "libpng version 1.6.2beta02 - April 18, 2013\
       Copyright (c) 1998-2013 Glenn Randers-Pehrson\
       Copyright (c) 1996-1997 Andreas Dilger\
       Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.";
@@ -2275,7 +2275,10 @@
       png_icc_check_tag_table(png_ptr, colorspace, name, profile_length,
          profile))
    {
-      png_icc_set_sRGB(png_ptr, colorspace, profile, 0);
+#     ifdef PNG_sRGB_SUPPORTED
+         /* If no sRGB support, don't try storing sRGB information */
+         png_icc_set_sRGB(png_ptr, colorspace, profile, 0);
+#     endif
       return 1;
    }