What version of GDB version is included in your Xcode?
The version on my system (Mountain Lion, XCode 4.5 is:

GNU gdb 6.3.50-20050815 (Apple version gdb-1822) (Sun Aug  5 03:00:42 UTC 2012)


Basically, 6.3 is the last version covered by the GPLv2 license, everything past that is subject to GPLv3. Apple does not distribute any GPLv3 software, presumably as it would seriously hinder their patent lawsuits. (this is also why OSX or XCode no longer ship with Samba or GCC newer than 4.2)

By the way, the last version of XCode for Snow Leopard is 4.2, but as far as I know this is only available in the downloads section to iOS or Mac developer program subscribers.