MFC	r256448, r257029;

Make di_blocks unsigned in UFS1 as is the case already for UFS2.
 Most of the code between UFS1 and UFS2 is shared so this change
 is pretty safe. Not only this makes UFS1 and 2 consistent but it
 also matches what NetBSD and MacOS X have for some years now.

UFS2: make di_extsize unsigned.
 di_extsize is the EA size and as such it should be unsigned.
 Adjust related types for consistency.

Reviewed by:	mckusick