Explicitly say that the mesh will be incorrect if the swapping failed

Fixed one more bug for degenerate, non-recombined extrusions, that could
lead to duplicate elements.

Fixed degenrate tets generation (oops!)

Fix 2 gcc warnings

- Fix element numbering in Extrude Point and Extrude Line
- Look for config files in $GMSH_HOME before $HOME

Fix whitespace in copyright headers

Cleanup Tree_Replace/Tree_Insert + better error detection in Read_Mesh.

typo

Add Layer on Extrude Point (phase 2 -- remove duplicates)

Indented all source files using utils/gmshindent

Fix all "uninitialized var" gcc warnings, even if they are bogus.

Added missing return

Updated copyright

New global volumic extrusion algorithm. New extrusion should now be the same (right or wrong!) as old extrusion...