I've fixed patch and news carefully by your notes.

To Jan Kratochvil, Yuanhui Zhang:

I've included absolute filename option to my patch.
	
Eli Zaretskii:

Here is an example of working with "relative filename" option:

$ gcc -Wall -g ~/Downloads/contrib/prog.c
$ ./gdb-7.4/gdb/gdb ./a.out

(gdb) backtrace
#0  main () at /home/unknown/Downloads/contrib/prog.c:3
(gdb) set backtrace filename-display relative
(gdb) backtrace
#0  main () at prog.c:3

As I remember the difference between "basename" and "relative" option
was explained some time ago in this thread.

~Eldar