gfc_deinit()
Incremental writer
Avoid typedef redefinition
Per-frame lossy setting
Avoid garbage return value when (s == 0 || n == 0)
Removed unused field from Gif_Colormap
Fixed custom gamma
Merge branch 'unusedfield'

* unusedfield:
  Removed unused field from Gif_Colormap
  Avoid garbage return value when (s == 0 || n == 0)
Merge branch 'customgamma'

* customgamma:
  Fixed custom gamma
Merge branch 'incremental'

* incremental:
  Per-frame lossy setting
  Avoid typedef redefinition
  Incremental writer
  gfc_deinit()