debug/gdb: update the version strings

Almost all versions have been renamed, but the gdb folks did not
setup legacy symlinks.

For more information, see this message:
http://sourceware.org/ml/gdb/2011-09/msg00002.html

Reported-by: ManuelStahl <manuel.stahl@iis.fraunhofer.de>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

 reporter_name="Gustavo Zacarias <gustavo@zacarias.com.ar>"

 reporter_url="http://sourceware.org/ml/crossgcc/2011-03/msg00028.html"

 reporter_comment=""