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

[sergiodj+buildbot@sergiodj.net]

*** TEST RESULTS FOR COMMIT 7dce57d1b5d8b26efd658069c7047eba57733eb4 ***

Author: Tim Wiederhake <tim.wiederhake@intel.com>
Branch: gdb-8.0-branch
Commit: 7dce57d1b5d8b26efd658069c7047eba57733eb4

Python: Introduce gdb.RecordGap class

As discussed here: https://sourceware.org/ml/gdb-patches/2017-04/msg00157.html

A gap is not an instruction and it should not pretend to be one.
gdb.Record.instruction_history is now a list of gdb.RecordInstruction and
gdb.RecordGap objects.  This allows the user to deal with Gaps in the record
in a more sane way.