1. Add support for hexagont box-type (BHex_t) in TEveBoxSet. See
tutorials/eve/boxset.C, new function boxset_hex().

2. Bugfix in TEveBoxSet -- box set did not work with TEnv setting of
`OpenGL.UseDisplayLists 0`.

3. Memory leak fix in TEveGeoShapeProjected -- TBuffer3D member fBuff was
not freed in destructor.