force yyflush when closing a file: this fixes the old parsing bug when a file ends in a // comment without a newline

- fixed MED node ordering
- polished 64 bit Cocoa Mac OS X FLTK version
- updated copyright

recoded way to create boundary layers using explicit extrusion directions from vector post-processing view

Adds an option to switch elementary and physical tags in loaded meshes, and fixes a bug with geo-mesh matching.

(which use the filename to guess which data file to read). Laurent's patch would set 
the filename to the last merged file, whereas we currently want the file name to be 
set to the projet file, i.e., the first merged file.

We should maybe think a bit harder about how to deal with this (maybe each Merge can 
set the fileName, but OpenFile takes precedence?)

* issue error for zero volume elements in FEA export
* reset element number between 2D/3D in FEA export

- partial fix for skipping empty time steps

 bar: it's not dynamic in fltk 1.1)

- invert #define logic (HAVE_MESH, HAVE_POST, HAVE_SOLVER, ... instead of HAVE_NO_MESH,
  HAVE_NO_POST, HAVE_NO_SOLVER)