Fix more portability issues with casts to Size when using off_t

This should tame the beast, as there are no other places where off_t is
used in the new error messages.

Reported again by longfin, which complained about walsender.c while I
spotted the other two ones while double-checking.

src/backend/replication/logical/snapbuild.c

@@ -1737,7 +1737,8 @@ SnapBuildRestore(SnapBuild *builder, XLogRecPtr lsn)
 		else
 			ereport(ERROR,
 					(errmsg("could not read file \"%s\": read %d of %zu",
-							path, readBytes, SnapBuildOnDiskConstantSize)));
+							path, readBytes,
+							(Size) SnapBuildOnDiskConstantSize)));
 	}
 
 	if (ondisk.magic != SNAPBUILD_MAGIC)

src/backend/replication/slot.c

@@ -1422,7 +1422,7 @@ RestoreSlotFromDisk(const char *name)
 			ereport(PANIC,
 					(errmsg("could not read file \"%s\": read %d of %zu",
 							path, readBytes,
-							ReplicationSlotOnDiskConstantSize)));
+							(Size) ReplicationSlotOnDiskConstantSize)));
 	}
 
 	/* verify magic */

src/backend/replication/walsender.c

@@ -509,7 +509,7 @@ SendTimeLineHistory(TimeLineHistoryCmd *cmd)
 		else if (nread == 0)
 			ereport(ERROR,
 					(errmsg("could not read file \"%s\": read %d of %zu",
-							path, nread, bytesleft)));
+							path, nread, (Size) bytesleft)));
 
 		pq_sendbytes(&buf, rbuf, nread);
 		bytesleft -= nread;