graphics/giflib: Update to 5.1.2

• Code hardening using reallocarray() from OpenBSD.

• Sanity check in giffilter catches files with malformed extension records Fixes SourceForge bug #63: malformed gif causes segfault in giffilter.

• Inexpensive sanity check in DGifSlurp() catches malformed files with no image descriptor. Fixes SourceForge bug #64: malformed gif causes crash in giftool.

• Fix SourceForge bug #66: GifDrawBoxedText8x8() modifying constant input parameter.

• Bail out of GIF read on invalid pixel width. Addresses Savannah bug #67: invalid shift in dgif_lib.c

• Fix SourceForge bug #69: #69 Malformed: Gif file with no extension block after a GRAPHICS_EXT_FUNC_CODE extension causes segfault (in giftext).

• Fix SourceForge bug #71: Buffer overwrite when giffixing a malformed gif.

• Fix SourceForge bug #73: Null pointer deference in gifclrmap (only reachable with malformed GIF).

• Fix SourceForge bug #74: Double free in gifsponge under 5.1,1, for any valid gif image.

• Fix SourceForge bug #75: GAGetArgs overflows due to uncounted use of va_arg.

• Sanity check in giffix catches some malformed files. Addresses SourceForge bug #77: dgif_lib.c: extension processing error

MFH: 2016Q1
Security: CVE-2015-7555