use pr -n -t instead of non-standard cat -n

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@10677 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

configure

@@ -178,7 +178,7 @@ log(){
 
 log_file(){
     log BEGIN $1
-    cat -n $1 >>$logfile
+    pr -n -t $1 >>$logfile
     log END $1
 }