Removed GSL dependency. Gmsh now uses blas and lapack for linear algebra
stuff.

moved all string options to std::string

*****************************************************************
WARNING: this has the potential to break things in subtle ways...
         PLEASE TEST AND REPORT ANY WEIRDNESSES
*****************************************************************

Amazingly, I have discovered a potentially serious bug in the routines
which perform edge collapse in the BDS_Mesh.

Owing to this, it is possible for a point to collapse onto a linear
boundary creating slivers (triangles with collinear points).

The problem is that the sides of the triangle, a and b, are not
recalculated after the point is moved.  Thus, area_final and area_init
are always equal!  So the test for slivers is defeated.

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

that the 2 steps are orthogonal
* added full-hexa subdivision algo

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

- added automatic transfinite corner selection for volumes

window with experimental tree browser

fix for "implicit" transfinite surfaces

move integration routines to Numeric/

in-house of blas/lapack)

without recompiling

fix recombine with embedded edges