Cleanup of various annoyances found during code audit.

git-svn-id: http://mancubus.net/svn/hosted/eternity/trunk@2749 86ba831e-150c-0410-ab35-e06eaae15ed9
Fix for "bad music number" message when playing Doom 2 maps with no assigned music and map numbers greater than 35. Also added much-needed eclamp macro.

git-svn-id: http://mancubus.net/svn/hosted/eternity/trunk@2750 86ba831e-150c-0410-ab35-e06eaae15ed9