[binutils-gdb/gdb-8.0-branch] Python: Introduce gdb.Instruction class

[sergiodj+buildbot@sergiodj.net]

*** TEST RESULTS FOR COMMIT ac7d85722af3e8a4db69940b77b82ca173ba3877 ***

Author: Tim Wiederhake <tim.wiederhake@intel.com>
Branch: gdb-8.0-branch
Commit: ac7d85722af3e8a4db69940b77b82ca173ba3877

Python: Introduce gdb.Instruction class

This adds a generic instruction class to Python and has gdb.RecordInstruction
inherit from it.