Enhancements to ppss related code (thanks Stefan).

Enhancements to ppss related code (thanks Stefan).
* progmodes/python.el (python-indent-context)
(python-indent-calculate-indentation, python-indent-dedent-line)
(python-indent-electric-colon, python-nav-forward-block)
(python-mode-abbrev-table)
(python-info-assignment-continuation-line-p): Simplified checks
for ppss context.
(python-info-continuation-line-p): Cleanup.
(python-info-ppss-context): Do not catch 'quote.
(python-info-ppss-context-type)
(python-info-ppss-comment-or-string-p): Simplify.