tests: fix a test on 32-bit builds
tests: fix a test on 32-bit builds

We were trying to squeeze 64-bit test vectors into gsize, which is fine
on 64bit systems but doesn't work very well on 32-bit.

Change that to a guint64.

Distrotech/glib,MathieuDuponchelle/glib,Distrotech/glib,ieei/glib,johne53/MB3Glib,Distrotech/glib,mzabaluev/glib,ieei/glib,mzabaluev/glib,ieei/glib,endlessm/glib,Distrotech/glib,ieei/glib,ieei/glib,MathieuDuponchelle/glib,johne53/MB3Glib,endlessm/glib,MathieuDuponchelle/glib,johne53/MB3Glib,MathieuDuponchelle/glib,endlessm/glib,mzabaluev/glib,Distrotech/glib,mzabaluev/glib,MathieuDuponchelle/glib,mzabaluev/glib,endlessm/glib,endlessm/glib,johne53/MB3Glib,johne53/MB3Glib,johne53/MB3Glib