enable new Delaunay for plane surfaces

experimental: don't use it for now

- changed '-convert' syntax to process multiple files at once

- added lateral entities in list returned by extrusion commands

- preliminary work to interface more parser functions with general
  GEntities

- we can now export simple GModels as.geo files (points, straight line
  segments, plane surfaces, ruled surfaces and volumes are treated
  correctly; all non-straight-line curves are exported as splines; all
  non-plane/ruled surfaces are not exported)

- tentative fix for the unv export problem reported on the mailing
  list (fprintf() buggy on some machines??)

- new IO (both read and write) for structured grids using the NASA
  Plot3D format (for Olivier)

- temporary fix for creation of second order vertices on periodic
  curves and periodic surfaces

- speedup 2nd order vertex creation

- never create MFaceVertices if we don't know the parametric
  coordinates (this will screw up the 2nd order algo!): create
  MVertices instead

- fixed u,v coords of vertices after elliptic smoother in
  meshGFaceTransfinite

- added "-format msh1" and "-format msh2" shortcuts to quickly
  select the version of the msh format from the command line +
  added "med" and "cgns" formats

- moved gui guidelines in separate file

better configure for MED

- added exception to GPL for triangle/tetgen
- fixed some command line switches
- added option to antialiasing OpenGL rendering

- new option Geometry.Tolerance (or -tol on the command line) to set the
tolerance for the old CAD engine, for OCC healing and for STL import

- removed more unused options

better names for mesh algo #defines

OpenProblem -> OpenProject
MergeProblem -> MergeFile

more on clcurv options

new option to compute char lengths from curvature + removed most unused mesh options

remove aniso + old extrude from interface

more occ work

spec fltk theme with -theme + minor tweaks

- finished Nastran BDF implementation (read+write in all BDF formats:
  free field, small field & long field)
- improved UNV and Medit import
- added detection of bad vertex indices in all import routines
- fixed bug in 2nd order quad constructor

Implemented new binary MSH file format (both read and write).

A 250Mb mesh file (6 million tetrahedra) is now read or written to disk in
less than 10 seconds (on my powerbook's slow hard drive).

minimize the number of files that include GmshVersion.h: it's annoying to
recompiletoo many files just because the version string changes

moved most OS-dependent functions in OS.cpp

- new button under the graphic window to temporarily disable mouse
  selection (speeds-up redrawing of very large models + permits to
  rotate/zoom-in a model in selection mode even when the whole screen
  is full of selectable entities--e.g. a surface mesh)

- new "lasso" selection mode (to select entities using the same kind
  of lasso as the lasso zoom: just Ctrl+click, then drag the mouse in
  selection mode; the shortcuts are the same as for the lasso zoom)

- it is now possible to unselect entities using the middle mouse button
  (only for the creation of physicals at the moment; not sure if it's
  useful in the other cases)

- new button in visibility browser to invert the current selection
  (very useful e.g. when multiple physical entities are associated
  with a given elementary entity, in order to "peel" away the model
  when adding new physicals; cf. philou)

- changed meaning of Escape shortcut (cancel lasso or toggle mouse
  selection) + restore standard fltk Escape handling for all dialog
  windows

- updated copyright string

- new mesh label mode (coordinates); all label types are now also
  available for mesh vertices

- added option in 'Print Option' dialog to disable printing of help
  strings

- added a comment string with the date when creating a new file

- new snapping grid for adding points in the GUI

Don't reinitialize the symbol tree in OpenFile.

(We don't reinitialize the option database, so why should we reinitialize
the variables? Using a single global symbol tree we can again define
variables with -string "" on the command line.)

use it now with -partition N for N partitions
only works with tets and triangles
output should be added (useless for now)

simpler tetgen integration by Jozef Vesely

generalized the solver interface to allow permanent listening on a
socket for whoever wants to connect (gmsh -listen)

the polling should also be less CPU hungry in this new version

next step is to add new commands to the protocol so that solvers can
directly transmit data to merge (geometry, mesh, etc.) in addition to
messages and filenames