Issue 1730: Documentation corrections for os module

I saw a minor inconsistency in the documentation of the os module and
then somehow ended up proof-reading the whole file :). The result of
this is attached as a patch against trunk.

Summary of the changes:

- Use the imperative tense in method descriptions
- Some more links using semantic markup
- Added example for file.seek
- Consistently use "" instead of '' in text
- or-ed, OR'd replaced with ORed
- bit-wise replaced with bitwise

Diffstat for the patch::

 Doc/c-api/newtypes.rst        |    2 
 Doc/library/fcntl.rst         |    2 
 Doc/library/functions.rst     |    2 
 Doc/library/msvcrt.rst        |    2 
 Doc/library/os.rst            |  155
+++++++++++++++++++++---------------------
 Doc/library/stdtypes.rst      |    9 +-
 Doc/library/winsound.rst      |    2 
 Doc/reference/expressions.rst |   18 ++--
 Lib/test/test_doctest.py      |    2 
 Modules/fcntlmodule.c         |    2 
 10 files changed, 101 insertions(+), 95 deletions(-)

I hope the changes are ok.

Thanks, committed as r59744!