[Python-mode] Python-mode guess-indent API change

[Andreas Röhler]

Hi Barry, hi all,

with resp. to a possibly reduced complexity
IMO Python-mode should not guess `py-indent-offset' when loading already.

It simply makes no sense to pick that from one spot, as every block may 
have a different one.

OTOH when one of the functions needing it like `py-compute-indentation' 
is called, all these functions can't used pre-calculated indents anyway 
- for the very reason.

See a bug report lp:902890 requiring it though.

WDYT?

Andreas