debug/gdb: pump gdb to version 7.7

pump gdb to version 7.7

Signed-off-by: '"Daniel Zimmermann" <netzimme@gmail.com>'
[yann.morin.1998@free.fr: remove superfluous empty lines]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Message-Id: <a1bcc8a58a4613f0b8bf.1392475799@haus-VirtualBox>
Patchwork-Id: 320657

 reporter_name="YEM"

 reporter_url="http://ymorin.is-a-geek.org/"

 reporter_comment=""