optimize 2d iso plots with vertex arrays

polih previous commit

2 big optimizations for meshes that contain a lot of line elements:

- speed up Read_Mesh (by introducing temp tree in curves)
- use vertex arrays for lines in mesh drawing code

update to latest gl2ps

fix warning

make the extrusion stuff work with SimplexBase too

fix warning

make the code compile on Mac OS X 10.4 (gcc 4.0.0)

- removed the "Dirty" flags in the CAD data structures

- when reading the mesh from an entity that has no CAD, create a "discrete"
  CAD entity

- remove the drawing of discrete entities that don't have a BDS
  representation during the geometry drawing

make it compile on my mac

removed remaining Discrete Line/Surface stuff

add entries about Visibility, Clipping and Transparency

two more fl_ask -> fl_choice

initialize bds=0 by default, so that at least the code does not crash when
doing normal things ;-)

removed "interactive aniso contruction" option from the GUI (to make some \
space for the "quad algorithm" option in the panel)

add link to pdf tutorial

typo

remove the '-bin' for getdp post-pro (for patrick)

link to GUI tutorial

force focus on OpenGL window when adding points

- fixed a couple of warnings

- JF: bds.classify crashes in recur_tag on simple examples (demos/sphere-stl.stl)

small script to test handling of many (e.g. 5000) views

Changed the initial allocation from
    liste->nmax = ((n - 1) / liste->incr + 1) * liste->incr,
which does not allow us to allocate lists smaller than iste->incr, to
    liste->nmax = n;

With this change, when we do "List_Create(1, N, sizeof(blah))", we
initially only allocate sizeof(blah) instead of N*sizeof(blah).