Merged revisions 70801,70809 via svnmerge from

Merged revisions 70801,70809 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk

The merge ran into a lot of conflicts because dicts were replaced with
sets in the Python 3 version of the symbol table.

........
  r70801 | jeremy.hylton | 2009-03-31 09:17:03 -0400 (Tue, 31 Mar 2009) | 3 lines

  Add is_declared_global() which distinguishes between implicit and
  explicit global variables.
........
  r70809 | jeremy.hylton | 2009-03-31 09:48:15 -0400 (Tue, 31 Mar 2009) | 14 lines

  Global statements from one function leaked into parallel functions.

  Re http://bugs.python.org/issue4315

  The symbol table used the same name dictionaries to recursively
  analyze each of its child blocks, even though the dictionaries are
  modified during analysis.  The fix is to create new temporary
  dictionaries via the analyze_child_block().  The only information that
  needs to propagate back up is the names of the free variables.

  Add more comments and break out a helper function.  This code doesn't
  get any easier to understand when you only look at it once a year.
........