Copy inspect.py from the standard library.

It uses 'tokenize', and we don't want 2 copies of that in the OPy
binary.  Instead we use pgen2/tokenize.py.

Use imports relative to the repo root.  Otherwise unit tests and
bin/opyc won't both work.

opy/byterun/pyobj.py

@@ -3,10 +3,11 @@

import collections
import dis
import inspect
import sys
import types

from opy.lib import inspect


def debug1(msg, *args):
  if args:

opy/byterun/pyvm2.py

@@ -4,7 +4,6 @@

from __future__ import print_function, division
import dis
import inspect
import linecache
import operator
import repr as repr_lib  # Don't conflict with builtin repr()

opy/callgraph.py

@@ -6,13 +6,14 @@

import collections
import dis
import inspect
import os
import sys

import __builtin__  # For looking up names
import types

from .lib import inspect

from core import util
log = util.log