Merge branch 'po/size-t-for-vs'

On platforms where ulong is shorter than size_t, code paths that shifted 1 or 1U to the left lacked the necessary cast to size_t, which have been corrected. * po/size-t-for-vs: object-file.c: LLP64 compatibility, upcast unity for left shift diffcore-delta.c: LLP64 compatibility, upcast unity for left shift repack.c: LLP64 compatibility, upcast unity for left shift