Fix some dependencies + enable GSL (so that more people test it).

This is a pretty big commit.

- The Numerical Recipes routines have been moved to their own
subdirectory: NR/

- These routines are now completely optional. Configure will
determine if they have to be compiled in (if it's a non-free version
of Gmsh) or if we should use the GSL routines instead.

- The GSL routines are there. Well, sort of. The SVD stuff works
great, but the minimization routines still need more work. The whole
infrastructure is there, though: we can already compile a fully GPL
compliant version of Gmsh by removing the NR subdirectory (or by
specifying --enable-gsl to configure).

- I also simplified the options passed to the compiler (OPTIM and
FLAGS).

That's all for today folks...

Don't use LITTLE_ENDIAN, it may be defined on Macs and cause the
colormap problems. Define and test _BIG_ENDIAN instead.

Change NODLL to _NO_DLL

Clean up VERSION_FLAGS and OS_FLAGS (use HAVE_FLTK instead of _FLTK,
remove _BLACKBOX, etc.)

Fix triangle dependency

New makefile system based on autoconf. Only tested on Linux right now.

sgi, take 3

Again for sgi

F$%k, the sgi compiler does not like initilizations with
non-constant parameters.

bump version to 1.37.0: system calls on Windows are now correctly implemented using the CreateProcess Windows API

Updated copyright

Generalized the LevelSet class for views with more than one time step.

Remove unused virtual

Missed the make depend

Commit some old stuff I had lying around on my machine.