golang: Don't keep test programs inside golang/ dir

Python adds dirname of run program to sys.path . This way when
golang_test_goleaked.py runs it can import modules located under golang/
just by their name. Until now this was not noticed, but in the next
patch we are going to add golang.time module and if test program is run
with golang/ in sys.path just plain `import time` won't import time from
stdlib and instead import time from golang/ .

Such behaviour can be mitigated by doing `from __future__ import
absolute_import` and we do that, including in golang_test_goleaked.py
(see 81dfefa0 "*: __future__ += absolute_imports; Use unified __future__
everywhere"). However that does not prevent modules - even modules from
stdlib - who are doing `import time` and not doing future
absolute_import to import golang's time instead of stdlib. For example
on PyPy2 threading imports time and then the test breaks:

  Traceback (most recent call last):
    File "/home/kirr/src/tools/go/pygolang/.tox/pypy-thread/site-packages/golang/golang_test_goleaked.py", line 24, in <module>
      from golang import go, chan
    File "/home/kirr/src/tools/go/pygolang/.tox/pypy-thread/site-packages/golang/__init__.py", line 38, in <module>
      import inspect, threading, collections, random, sys
    File "/usr/lib/pypy/lib-python/2.7/threading.py", line 15, in <module>
      from time import time as _time, sleep as _sleep
    File "/home/kirr/src/tools/go/pygolang/.tox/pypy-thread/site-packages/golang/time.py", line 30, in <module>
      from golang import go, chan, select, default, nilchan, panic
  ImportError: cannot import name 'go'

-> Move the test program into a directory different from golang/ to
avoid this trap.

MANIFEST.in

 include COPYING README.rst CHANGELOG.rst tox.ini
 recursive-include golang/testdata *.py
+recursive-include golang/testprog *.py
 recursive-include gpython/testdata *.py

golang/golang_test.py

@@ -44,7 +44,7 @@ def test_go():
         pathv.append(envpath)
     env['PYTHONPATH'] = ':'.join(pathv)
 
-    subprocess.check_call([sys.executable, dir_golang + "/golang_test_goleaked.py"],
+    subprocess.check_call([sys.executable, dir_golang + "/testprog/golang_test_goleaked.py"],
             env=env)