Changed some allocations to xcalloc.

src/modules/Image/encodings/ilbm.c

src/modules/Math/transforms.cmod

src/modules/_Charset/charsetmod.c

src/modules/_Charset/iso2022.c

src/post_modules/GL/auto.c.in

src/post_modules/GTK1/source/gtkobject.pre

src/post_modules/Nettle/nettle.cmod