(Bug 5323) Disable parsing of external entities in synsuck and the importer

* creates the DW::XML::RSS/DW::XML::Parser modules to replace their
  XML::* equivalents. Works basically the same, just with a tighter
  configuration
Always use LJ::challenge_check_login
Merge branch '_always-use-challenge_check_login' into release-1.20

* _always-use-challenge_check_login:
  Always use LJ::challenge_check_login
Merge branch '_xml-entity-sec-bug5323' into release-1.20

* _xml-entity-sec-bug5323:
  (Bug 5323) Disable parsing of external entities in synsuck and the importer
Fix error
Merge pull request #733 from afuna/syntax-error-approve

Fix error
Fix whitespace
Fix nested comments not showing up sometimes

We were popping from the original comments array... so in
one-column-split, after processing the page summary module, there were
no more comment replies to be printed. Oops. Fixed by working on a copy
of the original array.
Merge pull request #734 from afuna/nested-comments-in-one-column-split

Fix nested comments not showing up sometimes
Hush various warnings
Merge pull request #735 from afuna/hush-various-warnings

Hush various warnings
Better error message when cleaning out purged members

Instead of saying "removed: (list of all roles)" which may or may not be
true, just say that they were removed from the community
Don't try to convert "0000-00-00" to a time

Occasionally shows up in the logs as "Month '-1' out of range 0..11 at
cgi-bin/LJ/Time.pm line 84"
[#740] Fix POSTing of changeemail

* rely on $r->did_post, instead of a submit mode
* if on an https page, submit to https
Merge pull request #740 from afuna/changeemail-post-bug-740

Fix "change email" function
Merge pull request #736 from afuna/tweak-error-message-purge

Better error message when cleaning out purged members
Merge pull request #737 from afuna/mysqldate_to_time-0000-00-00

Don't try to convert "0000-00-00" to a time
Don't print out too many closing divs

Make sure not to update the $prev_depth variable past MAX_NESTED_DEPTH
(because the div should be closed immediately).
Merge pull request #741 from afuna/fix-nested-closing-div-comments

Don't print out too many closing divs
Add contextual hover menu to foundation pages