Patch by Andrei Dorian Duma.

Original patch by Vajrasky Kok, further improved (I hope) by me.

Use aslo PyUnicode_FromFormat() to format the line so only one call to
PyFile_WriteObject() is needed. tb_displayline() of Python/traceback.c has
similar implementation.

asyncio: Add close() back to Unix selector event loop, to remove all signal handlers. Should fix buildbot issues.

The comment is meaningless since changeset 4e985a96a612.

_PyUnicode_CompareWithId() is faster than PyUnicode_CompareWithASCIIString()
when both strings are equal and interned.

Add also _PyId_builtins identifier for "builtins" common string.

Replace _PyUnicode_AsString()+strcmp() with PyUnicode_CompareWithASCIIString().

string "flush" to call the flush method

instead of literal "get" string

literal string

instead of creating temporary Unicode string objects

Add also more identifiers in pythonrun.c to avoid temporary Unicode string
objets for the interactive interpreter.

"modules" once

to only create the "displayhook" string once

identifier for the "__abstractmethods__" string

PyDict_DelItemString() but using an identifier for the key

"Py_Repr" dictionary key

Only decode the filename once. PyRun_InteractiveOneObject() uses an identifier
for "<string>" string, so the byte string is only decoded once.

key from sys._xoptions

dictionary key and only decodes "\n" string once to write a newline.

So "builtins" and "\n" are only decoded once from UTF-8, at the first call.

- confusing line_offset parameter -> first_line parameter
- systematically test and fix new file parameter
- remove redundant Bytecode.show_info() API
- rename Bytecode.display_code() to Bytecode.dis() and have it
  return the multi-line string rather than printing it directly
- eliminated some not-so-helpful helpers from the bytecode_helper
  test support module

Also fixed a longstanding defect (worked around in the test suite)
where lines emitted by the dis module could include trailing white
space. That no longer happens, allowing the formatting tests to be
simplified to use plain string comparisons.