Encapsulate toolkit-dependent global drawing functions in new
drawContextGlobal class, and add a static drawContextGlobal to
drawContext, with a default version that does nothing.

This allows to have a completely virtualized drawing system: we can
now ship a library with a fully working graphic system, indepedent of
the widget toolkit. A client code just needs to subclass
drawContextGlobal to get working graphics (see
e.g. api_demos/mainAntTweakBar.cpp)

- pretty print code

- better (?) check for MKL without Fortran on MSVC

Changed set(GMSH_API by list(append GMSH_API
Added DILevelset.h to GMSH_API if ENABLE_DINTEGRATION

CMakeLists.txt to set the oofelie flags

re-committing work from last two days after server crash:

- refactored old Geo code (new/delete)
- moved DrawPlugin to Plugin
- move from matheval to mathex
- move from Flu_Tree_Browser to Fl_Tree
- fixed crash in Triangulate plugin

- make sure we don't package the binary dir in make package_source
- fix GMSH_VERSION in Info.plist
- move last few README to README.txt
- added all remaining un-committed converters from mailing list into utils/

- moved GUI to FlGui + added experimental QGui to test Qt

- fixed most MSVC and gcc compiler warnings

- converted some remaining tabs to whitespace (that's why the patch is
  so large; please try to remember to indent with 2 spaces and not
  tabs when you commit stuff to CVS)

- merged modified patch from Konstantinos Poulios to allow saving
  physical/partition as element tags in mesh formats that don't
  support them natively