Include stddef.h because size_t is used in GCB API
Include stddef.h because size_t is used in GCB API

Signed-off-by: Alexander Strasser <e0a974c7f0d966b3a4c849485101d154306c99c7@gmx.net>

rcancro/giflib,rcancro/giflib,rcancro/giflib,cention-sany/libgif,cention-sany/libgif