(py-compute-indentation): Changes to the `t' condition which affect

indetnation of normal statements: The regular expression that searches
for indenting comment lines has been changed to not require a
space/tab after the first `#'.  We then explicitly look for
py-block-comment-prefix depending on the value of
py-honor-comment-indentation.

I think this more accurately reflects the documentation for
py-honor-comment-indentation.