Remove obsolete util_opy.py.

We are now sharing core/util.py.

Surprisingly, this introduced a change in the compiled output of
_regtest/src/util_opy.py!  The compilers source code leaks through to
the thing being compiled!

I think this must because of the way consts are handled.  When you are
compiling a const, it might be looked up in global interpreter state.
If the same constant is not in the interpreter because util_opy.py is no
longer imported, then the results can be different.

Haven't fixed this diff yet:

$ ./regtest.sh verify-golden
--- _regtest/dis-md5.golden.txt 2018-03-17 20:12:45.245834622 -0700
+++ -   2018-03-17 23:11:28.941012975 -0700
@@ -34,7 +34,7 @@
    823 5a440f929760bbd1f36d3bfa4b3779f8 _tmp/regtest/core/word_eval_test.pyc
    834 4a3120879710a4fd9f9d6039e4dade55 _tmp/regtest/opy/compiler2/consts.pyc
    845 0eea196e032e82f3ddc932265ce3b640 _tmp/regtest/asdl/arith_ast.pyc
-   909 b82e6bdb2652220742231fbe2bd14221 _tmp/regtest/opy/util_opy.pyc
+   899 0dd9d5f5018f43b257a438ad9680d1c1 _tmp/regtest/opy/util_opy.pyc
   1010 338f3f9966140f857e952f610a3918db _tmp/regtest/spec/bin/read_from_fd.pyc

bin/opy_.py

@@ -13,9 +13,9 @@
from core import args
from core import util

from opy.util_opy import log
from opy import opy_main

log = util.log

# TODO: move to quick ref?
_OPY_USAGE = 'Usage: opy_ MAIN [OPTION]... [ARG]...'

opy/count.sh

@@ -15,7 +15,7 @@ _count() {
# transformer -> ast -> compiler -> byte code
all() {
  echo COMMON
  echo opy_main.py util_opy.py | _count
  echo opy_main.py | _count
  echo

  echo LEXER, PARSER GENERATOR, AND GRAMMR

opy/opy_main.py

@@ -29,10 +29,9 @@
# Disabled for now because byterun imports 'six', and that breaks the build.
#from .byterun import execfile

from .util_opy import log

from core import args
from core import util
log = util.log


# From lib2to3/pygram.py.  This takes the place of the 'symbol' module.

opy/regtest.sh

@@ -63,9 +63,10 @@ manifest() {

# 19 seconds on lisa.  This should be a benchmark.
compile() {
  local pat=${1:-}
  local dest=_tmp/regtest
  mkdir -p $dest
  time manifest | ./build.sh compile-manifest $dest
  time manifest | egrep "$pat" | ./build.sh compile-manifest $dest
}

checksum() {