Updated gifsicle to 1.88.

Version 1.88  1.Jul.2015

* Fix bug where long comments were read incorrectly. Reported by
  kazarny.

* Add --no-ignore-errors option.

Version 1.87  9.Dec.2014

* Always optimize as if the background is transparent. This fixes some
  rare bugs reported by Lars Dieckow.

* Fix --crop issue with must-be-preserved frames that are out of the
  crop window.

Version 1.86  14.Oct.2014

* Further fix --rotate + --crop.

Version 1.85  14.Oct.2014

* Greatly improve optimization time for images with many colors.

* Add --no-extensions (with the s) and document those options more.

* Fix bug in interaction of --resize and --rotate reported by Michał
  Ziemba.

Version 1.84  29.Jun.2014

* Correct optimizer bug that affected GIFs with 65535 or more total
  colors. Reported by Jernej Simončič.

Version 1.83  21.Apr.2014

* Correct bug in custom gamma values reported by Kornel Lesiński.

* Update Windows build.

Version 1.82  27.Mar.2014

* Correct bug in `mix` sampling method reported by Bryan Stillwell.

Version 1.81  24.Mar.2014

* Correct bug in `mix` sampling method reported by Bryan Stillwell.

Version 1.80  18.Mar.2014

* Bug fixes and improved error messages.

Version 1.79  17.Mar.2014

* Major improvements in image scaling. Work sponsored by Tumblr via
  Mike Hurwitz.

** Add new resize sampling methods `mix`, `box`, `catrom`, `mitchell`,
  `lanczos2`, and `lanczos3`, selectable by `--resize-method`. The
  `catrom` filter often gives good results; the slightly faster `mix`
  method (a bilinear interpolator) is now the default. These new
  sampling methods consider all of the image's input colors when
  shrinking the image, producing better, less noisy output for most
  images.

** Add `--resize-colors`, which allows Gifsicle to enlarge the palette
  when resizing images. This is particularly important when shrinking
  images with small colormaps---e.g., shrinking a black-and-white
  image should probably introduce shades of gray.

* Support extensions such as XMP4 in which extension packet boundaries
  matter. Reported by `ata4`.

* Many bug fixes, especially to cropping. Thanks to Tumblr and to
  Bryan Stillwell, Tal Lev-Ami, "Marco," and others.

(wiz)