Another Variant for detecting if a connection is closed

If there is a closed attribute on the connection and
it is true, return true. Implements a todo in the code
and helps in one specific disconnect case where it previously
did not match because the error message was "unknown error".
- a rework of doc layout and nav:
  - reduce the real estate for the top nav; move the search box
    into the top yellow box, close in space
  - use a new CSS/js approach such that the top toolbar freezes from
    scrolling at the top of the page.  The left nav scrolls independently
    of the content pane so that the local contents remain visible regardless
    of scrolling.   this approach is disabled on mobile where the dual scrollbars
    may be cumbersome (overall the site is not well designed for mobile).
Merge branch 'master' into rel_1_0
Merge branch 'master' into rel_1_0
Merge branch 'master' into rel_1_0
Merge branch 'master' into rel_1_0
Merge branch 'master' into rel_1_0
Merge branch 'master' into rel_1_0
Merge branch 'master' into rel_1_0
Merge branch 'master' into rel_1_0
Merge branch 'master' into rel_1_0
Merge branch 'master' into rel_1_0
Merge branch 'psycopg_disconnect' of https://github.com/dirkmueller/sqlalchemy
- The psycopg2 ``.closed`` accessor is now consulted when determining
if an exception is a "disconnect" error; ideally, this should remove
the need for any other inspection of the exception message to detect
disconnect, however we will leave those existing messages in place
as a fallback.   This should be able to handle newer cases like
"SSL EOF" conditions.  Pull request courtesy Dirk Mueller.
fixes #3021
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