- Merged revisions 1551-1597 from trunk, updating to GZDoom 1.8.0 and ZDoom 2.7.0 r4341.

git-svn-id: http://mancubus.net/svn/hosted/gzdoom/branches/doom64@1598 b0f79afe-0144-0410-b225-9a4edf0717df