small cleanups for 2.0.8

warning->error when trying to assign explicit reg ids in extrusions
+ add note in doc for this

tCircle and tCoherence were removed from the lexer? WTF?

Jonathan

background mesh. I've still to write some fields sub-class, but backward
compatibility should be ok now.
Jonathan
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prepare for named string expr

- 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)

fix syntax for hole carving

- boundary layer can now be generated by using a post-pro view for the
  normal field

- added more operations on lists in parser (FExpr * FExpr_Multi, etc.)

- new "hole carving" code to create extruded grids carved out around
  some surfaces (the resulting cavity can be filled with "grout" using
  the unstructured algos)

- check if bboxes of post-pro views are not == VAL_INF before adding
  them to the model bbox (bug report from Renaud Sizaire)

- fixed crash in LCM_xxx tensor drawing code when no tensor points are
  available. (This piece of code should be cleaned up further--no time
  for that now.)

- generalize Levelset plugins so that they work on point data sets

new boundary layer mesh generator

refactored smooth value/smooth normal code into single SmoothData.* file

added General.MinX, General.MaxX, etc. so that we can easily get the
min/max of a model (useful e.g. to create a box around an imported
STEP model)

added example of mixed step/geo model

include the geometrical entities defined in this script (since we
import THEM into GModel *after* we've parsed the file)

orientation bug in extrusion

- make it easier to build universal binaries on Mac
- remove unused arg in transform functions (an prepare the terrain for periodic meshes)

- added warning dialog before attempting to append a scripting
command to a non-geometry file

- fixed mean plane computation for periodic curves

- added headers + ramn indent on Attractor files

enhancement of gmsh Surfaces

JFR

fix shift/reduce conflict in parser (had to slightly modify embedding syntax)

corrected some bugs in 2d mesher & occ interface

- save physicals labels when saving unrolled geometries
- fixed crash in unrolled geo save (discrete points)
- Delete Physicals now also deletes the physicals in GModel
- removed unused rules and terminals in parser
- put at least one mid-point when meshing non-straight lines
  in OCC: this fixes most of the trivial 2d meshing problems

removed most unused, untested or non-working stuff in old CAD code

- bug fix: need to create temporary bounding box and compute CTX.lc
*during* parsing step until we fill the new db on the fly

(Some geo transforms in the parser use CTX.lc for tolerences. But
CTX.lc was always equal to 1 since we only do a SetBoundingBox on
GModel after parsing!)

- cleanup spline interpol (remove duplicate code)

OpenProblem -> OpenProject
MergeProblem -> MergeFile

Layers{N,1} can now be written simply as Layers{N}

deprecated -> warnings instead of errors

make default transfinite subdivision match old version to minimize
backward compat problems

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

curvature control is ok
divide and conquer algo has been cleaned up

more infrastructure for projection face gui

physical entities can now be defined using a string instead of a number (and
there is a new field $PhysicalNames in the .msh format to keep track of these
strings)