Cygwin is GONE!

- usleep takes microseconds
- work on c solver interf

"pure windows" version (without cygwin) is almost there: the solver
interface now works quite nicely using native Windodiows sockets and
the timers work too. There are still some bugs with binary files and
user-created functions in the parser.

replaced poll() with direct call to select(). This should help in getting
the solver interface eventually work on Windows without cygwin

add button in GUI to choose if we should always listen to incomming
connections requests

added example of interactive command line driver for Gmsh

- rename CLIENT_VIEW into CLIENT_MERGE_FILE
- new CLIENT_PARSE_STRING

characteristic lenghts, that would lead to HUGE meshes (this is one
of the most common causes for erroneous bug reports on the mailing list)

added support for empty lists (aa[] = {};) and concatenation of lists
(aa[] += {1,2,3};)

newsl and newll to get next available loop numbers

- recompute min/max in view after adaptation
- cleanup superfluous resets of TimeStepMin/Max

small fixes

fixing  orientation of adaptive triangles and quads

better heuristics for vertex array allocation (to get less horrible
performance on cygwin; the correct fix would be to do a preprocessing
step to precompute the actual number of primitives that are going to
be drawn... or even better: stop using cygwin alltogether)

ask confirmation to overwrite a mesh file when clicking on "Save Mesh"

call fl_register_images() explicitly (don't rely on loading the default
icons to initialize the extra image handlers)

Disable the End_Curve/End_Surface tests after point transformations
if Geometry.AutoCoherence=0. This is not perfect, but at least this
gives us a way to bypass these (very slow) tests for big models with
a lot of geometrical transformations (for which one would set
AutoCoherence to 0 anyway)

I borked the smooth plugin with my cleanups: this fixes it