fltkmain accidentally used optind instead of optndx. optind is
defined as an extern int in glibc but not on BSD systems.
This also broke passing a filename on command line.
For example forward/backward buttons are present on many mouses
but are not used by solvespace. This oops() caused solvespace to
crash whenever those buttons were (accidentally) pressed.
"There was some small but annoying bugs with the FLTK port:
-cursor disappear sometimes
-not all the area of the windows (graphic and text windows) is accessible
by the mouse after a re-size
-input widget for editing constraints value are not correctly placed"
The libslvs library and CDemo program can now be built by Autotools. A few
code changes were needed for this: C++ comments in C code had to be
converted, constraint.cpp required some massaging, and fltkutil.cpp needed
a stub for InitHeaps().
The SolveSpace top-level directory was getting a bit cluttered, so
following the example of numerous other free-software projects, we move the
main application source into a subdirectory and adjust the build systems
accordingly.
Also, got rid of the obj/ directory in favor of creating it on the fly in
Makefile.msvc.
