Use gdb.VERSION instead of parsing gdb.execute result (#467)
Use gdb.VERSION instead of parsing gdb.execute result (#467)

Yay, this is finally there:

```
>>> gdb.VERSION
'8.1.0.20180409-git'
```
anthraxx/pwndbg,cebrusfs/217gdb,anthraxx/pwndbg,anthraxx/pwndbg,pwndbg/pwndbg,pwndbg/pwndbg,disconnect3d/pwndbg,0xddaa/pwndbg,0xddaa/pwndbg,disconnect3d/pwndbg,cebrusfs/217gdb,cebrusfs/217gdb,cebrusfs/217gdb,disconnect3d/pwndbg,pwndbg/pwndbg,pwndbg/pwndbg,anthraxx/pwndbg,0xddaa/pwndbg