levels: Strip out GL_NODES data from E1M1.
levels: Strip out GL_NODES data from E1M1.

This is presumably used by certain source port(s) but isn't really
necessary. Strip this out so that we save 150KB from freedoom1.wad.

jmtd/freedoom,jmtd/freedoom,CWolfRU/freedoom,jmtd/freedoom,CWolfRU/freedoom