Fixed Bug #66901 php-gd 'c_color' NULL pointer dereference

Upstream https://bitbucket.org/libgd/gd-libgd/commits/463c3bd09bfe8e924e19acad7a2a6af16953a704

Notice: this fix don't manage monochrome/monovisual values
but just fix the security issue CVE-2014-2497
failing when trying to load such an image
NEWS