From The_E, niffiwan, m_m, and myself: Fix Mantis 2404.

Makes "$Weapon Model Draw Distance:" actually stop external weapon models from being drawn beyond that distance (modified by detail level).

git-svn-id: svn://svn.icculus.org/fs2open@11178 387891d4-d844-0410-90c0-e4c51a9137d3