Merged revisions 77477-77478,77481-77483,77490-77493 via svnmerge from

Merged revisions 77477-77478,77481-77483,77490-77493 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk

........
  r77477 | mark.dickinson | 2010-01-13 18:21:53 +0000 (Wed, 13 Jan 2010) | 1 line

  Add comments explaining the role of the bigcomp function in dtoa.c.
........
  r77478 | mark.dickinson | 2010-01-13 19:02:37 +0000 (Wed, 13 Jan 2010) | 1 line

  Clarify that sulp expects a nonnegative input, but that +0.0 is fine.
........
  r77481 | mark.dickinson | 2010-01-13 20:55:03 +0000 (Wed, 13 Jan 2010) | 1 line

  Simplify and annotate the bigcomp function, removing unused special cases.
........
  r77482 | mark.dickinson | 2010-01-13 22:15:53 +0000 (Wed, 13 Jan 2010) | 1 line

  Fix buggy comparison:  LHS of comparison was being treated as unsigned.
........
  r77483 | mark.dickinson | 2010-01-13 22:20:10 +0000 (Wed, 13 Jan 2010) | 1 line

  More dtoa.c cleanup;  remove the need for bc.dplen, bc.dp0 and bc.dp1.
........
  r77490 | mark.dickinson | 2010-01-14 13:02:36 +0000 (Thu, 14 Jan 2010) | 1 line

  Fix off-by-one error introduced in r77483.  I have a test for this, but it currently fails due to a different dtoa.c bug;  I'll add the test once that bug is fixed.
........
  r77491 | mark.dickinson | 2010-01-14 13:14:49 +0000 (Thu, 14 Jan 2010) | 1 line

  Issue 7632: fix a dtoa.c bug (bug 6) causing incorrect rounding.  Tests to follow.
........
  r77492 | mark.dickinson | 2010-01-14 14:40:20 +0000 (Thu, 14 Jan 2010) | 1 line

  Issue 7632:  fix incorrect rounding for long input strings with values very close to a power of 2.  (See Bug 4 in the tracker discussion.)
........
  r77493 | mark.dickinson | 2010-01-14 15:22:33 +0000 (Thu, 14 Jan 2010) | 1 line

  Issue #7632:  add tests for bugs fixed so far.
........