allow negative line loop number in surface definitions

Adding python solver interface from Carl Osterwisch <osterwischc@asme.org>.

The interface comes with a example python "solver" that converts an Abacus
result file (in CSV format) into Gmsh post-processing views. Very cool ;-)
Thanks Carl!

Fl_Double_Window is not really necessary for Main_Window

Create windows as Fl_Double_Window (double-buffered) instead of
Fl_Window. This makes the GUI "smoother" on Windows and Linux. The Mac
port of FLTK actually always uses Fl_Double_Window, even when one asks
for an Fl_Window...

typo

capitalize tab headers

%g->%.3g + use format also for 2d graphs

set default number format to %g, and use it to display the time value, too

more intuitive behaviour of geometry+mesh selection

better Tools->Visibility GUI

typo

- fixed the "unix socket name is one character short" problem on
MacOS and AIX. Unfortunately, this required the client code to be
slightly modified as well (and as a consequence, old versions of getdp
will for example not work with new versions of Gmsh on MacOs and
AIX). But it's better to do things "the right way" (TM) for people who
want to connect using different languages (Perl, Python).

- moved the GmshServer stuff in its own class

- added missing rules in parser makefile (so that the parser gets
  rebuilt automatically when one changes Gmsh.y or Gmsh.l)

ask if we should remove the temp files

small cleanup (+ remove solver link on webpage)

new "AliasWithOptions" command

use C++ example in doc instead of C

tiny cleanup

build solver examples with ${FLAGS}, so that on Windows they receive the
-mwindows argument

small modification to make the solver interface not block the GUI when the
solver runs without printing messages

don't include GmshClient

small cleanup

reorganized solver directory + added c++ solver example

enable use of x,y,z in general raise

nicer Offset GUI

better defaults for gen_raise expressions

trying to fix (void*)->(long) issue

- renamed "Duplicate View" into "Alias View" (suggested by Philippe;
  less confusing since "Duplicate" implies that we actually copy the
  data, which is not what we are doing)

- added general "on the fly" tranformation matrix option. This allows
  for very efficient visualization of aliased datasets with
  non-destructive rotations, symmetries, etc.

added option to use mencoder (to create mpeg4)

help should mention that iView and ExternalView have to be of the same
type (scalar, vector or tensor)

new plugins: Gradient, Curl and Divergence

re-introduced the ability to reverse the progression in 1D transfinite meshes
by specifying a negative line number (not sure why we removed this...)

move old (fixed) bug files to non-bug directories

update the colors in the reference view when we change the color scheme
(should fix the bug reported by Laurent)