gdk-pixbuf2: multiple issues

• CVE-2015-7673 (denial of service)

It has been discovered that under certain circumstances while scaling a
tga file a heap memory allocation may fail which is later used and leads
to a denial of service.

• CVE-2015-7673 (heap buffer overflow)

It has been discovered that under certain circumstances while scaling a
gif file a heap buffer overflow can occur. The cause of this issue was
that the integer data type was incompatible with the details of how
bitwise shifts were used.