Clean up a few more Inferno references.

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@9554 387891d4-d844-0410-90c0-e4c51a9137d3
This version string is not used for output filenames, it's more useful indicating to developers that this is a trunk build as opposed to an RC or final release.  Also, the same change wasn't made to the Xcode 3 project so they ought to match one way or another.

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@9555 387891d4-d844-0410-90c0-e4c51a9137d3