[docs] Update Curses HOWTO for 3.4 (issue 17700)

[ezio.melotti at gmail.com]

Just a few markup-related nitpicks :)


http://bugs.python.org/review/17700/diff/7840/Doc/howto/curses.rst
File Doc/howto/curses.rst (right):

http://bugs.python.org/review/17700/diff/7840/Doc/howto/curses.rst#newcode40
Doc/howto/curses.rst:40: appearance--and the curses library will figure
out what control codes
These should be --- (-- creates an EN dash).  Also the spacing around
them is not consistent (I'm not sure if there is a convention about it,
but I usually put a space before and after it).

http://bugs.python.org/review/17700/diff/7840/Doc/howto/curses.rst#newcode44
Doc/howto/curses.rst:44: `Urwid
<https://pypi.python.org/pypi/urwid/>`__.
A single trailing _ is enough to create links.

http://bugs.python.org/review/17700/diff/7840/Doc/howto/curses.rst#newcode143
Doc/howto/curses.rst:143: for i in range(0, 20):
range(20)?

http://bugs.python.org/review/17700/diff/7840/Doc/howto/curses.rst#newcode180
Doc/howto/curses.rst:180: Note that the coordinate system used in curses
is unusual.  Coordinates are always passed
This line is too long.  There are a few more long lines later.

http://bugs.python.org/review/17700/diff/7840/Doc/howto/curses.rst#newcode250
Doc/howto/curses.rst:250: update the data structure, and then call
:func:`doupdate` to update
All these can be turned into links by using :func:`~curses.doupdate`. 
IIRC there was also a way to specify the current module, so that it's no
longer necessary to keep adding ~curses in each role.

http://bugs.python.org/review/17700/diff/7840/Doc/howto/curses.rst#newcode436
Doc/howto/curses.rst:436: window method. After ``nodelay(1)``,
:meth:`getch` and :meth:`getkey`
nodelay(True)?

http://bugs.python.org/review/17700/diff/7840/Doc/howto/curses.rst#newcode480
Doc/howto/curses.rst:480: spaces.   Here's an example::
Extra space.

http://bugs.python.org/review/17700/diff/7840/Doc/howto/curses.rst#newcode488
Doc/howto/curses.rst:488: editwin = curses.newwin(5,30,2,1)
Spaces after commas.

http://bugs.python.org/review/17700/