- simplified background drawing (+added option to use jpeg/png image)
- better default clipping planes

what was causingthe uncomprehensible LNK1179 error ("duplicate
COMDAT") with MSVC.

No idea why.

HAVE_XXX defines.

This fixes three longstanding problems:

- the API was hard to use because some headers had HAVE_XXX ifdefs, so
  that cient codes had to know how the lib was compiled to compile
  themselves

- we had to do make clean after each ./configure, which erased too
  much (e.g. most of contrib)

- make depend could include unwanted stuff since it redefined FLAGS

added File->Clear + changed behaviour of File->New (now just adds a
new model)

allow smaller fonts for palettes (test with "-deltafontsize")

use display list for 3d arrows (approx. 2x speedup on my laptop for
large vector views) and spheres

removed static quadrics (wrong when \exists multiple gl contexts),
replaced with correct(?) init in drawContext

- fix bb computation to avoid model jumping around when adding points in z=0 plane
- pass interpol matrices as ref

There's no new functionality for now: PLEASE TEST THAT EVERYTHING
WORKS AS IT USED TO BEFORE.

multi-window & multi-coordinate system drawing.

There's no new functionality for now: PLEASE TEST THAT EVERYTHING
WORKS AS IT USED TO BEFORE.

CGNS I/O rewrite - alpha version