Restore ability to play internal demos through -playdemo which was accidentally lost during refactoring of WadDirectory for zip file support.

git-svn-id: http://mancubus.net/svn/hosted/eternity/trunk@2783 86ba831e-150c-0410-ab35-e06eaae15ed9
Changelog update for 12/24 and 12/25.

git-svn-id: http://mancubus.net/svn/hosted/eternity/trunk@2784 86ba831e-150c-0410-ab35-e06eaae15ed9
* Minor proofreading fixes for changelog
* Portal problem 1: need to scan thinker list for all Mobjs in a subsector when setting sector groupids, or NOSECTOR objects will be left out. This is incorrect.
* Portal problem 2: Mobjs should NOT clear groupid when they are removed. It needs to remain valid until other things stop referencing them.
* Portal problem 3: I don't want two definitions of the link getting functions. There's no advantage to inlining them only in release and then potentially forgetting to update one or the other implementation.

git-svn-id: http://mancubus.net/svn/hosted/eternity/trunk@2785 86ba831e-150c-0410-ab35-e06eaae15ed9
* Changes to error message reporting.
* Forgot to mention in previous commit: redacted old half-finished attempt at generalization of the EMAPINFO loader which was going to handle Hexen MAPINFO; implementation got cut off and then forgotten by my being hired in late June 2010. Have different plans now.

git-svn-id: http://mancubus.net/svn/hosted/eternity/trunk@2786 86ba831e-150c-0410-ab35-e06eaae15ed9