-Add support for ZDoom sector special 115 (instant kill) (bug 956).

git-svn-id: http://odamex.net/svn/root/trunk@3708 b0bcef46-2027-0410-bd56-ab726e9a1d04
-Use 64-bit intermediate calculations when resampling audio samples.
-Fixes integer overflows that lead to crashes (bug 950).

git-svn-id: http://odamex.net/svn/root/trunk@3709 b0bcef46-2027-0410-bd56-ab726e9a1d04