And a bandaid so that the output of "available space" is correct when

using -m and -g switches and "available space" is negative (i.e. when
the file system is already using the root-reserved minimum free space).

Obtained from:   Stefan Farfeleder <stefan@fafoe.narf.at>
PR:              bin/62536
Submitted by:    Peter van Dijk <peter@dataloss.nl>
Approved by:     grog (mentor), bde

bin/df/df.c

@@ -400,7 +400,8 @@ prthumanval(double bytes)
  */
 #define fsbtoblk(num, fsbs, bs) \
 	(((fsbs) != 0 && (fsbs) < (bs)) ? \
-		(num) / ((bs) / (fsbs)) : (num) * ((fsbs) / (bs)))
+		(num) / (intmax_t)((bs) / (fsbs)) : \
+		(num) * (intmax_t)((fsbs) / (bs)))
 
 /*
  * Print out status about a file system.