gdb: Improved interface to $percpu
gdb: Improved interface to $percpu

Now it can handle things like percpus declared in namespaces.

aclements/sv6,bowlofstew/sv6,bowlofstew/sv6,bowlofstew/sv6,aclements/sv6,aclements/sv6,bowlofstew/sv6,bowlofstew/sv6,aclements/sv6,aclements/sv6