smart_ulltoa5: emit small letters k,m,g... - makes top

more readable

libbb/xfuncs.c

@@ -323,7 +323,8 @@ void smart_ulltoa5(unsigned long long ul, char buf[5])
 		}
 		buf[2] = "0123456789"[v];
 		// see http://en.wikipedia.org/wiki/Tera
-		buf[3] = " kMGTPEZY"[idx];
+		// (small letters stand out better versus numbers)
+		buf[3] = " kmgtpezy"[idx];
 	}
 	buf[4] = '\0';
 }