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

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

Updated copyright

box of e.g. a view when merged in a script

Simplify error messages in parser a bit and change msg from ERROR to WARNING for list of shapes (less annoying when doing generic transformations, e.g. of points). Noticed this thanks to Genot Jean-Sebastien <JSGenot@HerouxDevtek.com>

compilation directives (cf. __APPLE__), were to rename the type
ColorTable to GmshColorTable and the function Palette to Palette1,
in order to avoid conflicts with Apple's QuickDraw.
Note that HFS is case-insensitive, which requires to have a fltk lib
name otherwise than libfltk.a (in the Mac version, the GL part is separate
anyway, so I've been using libfltk_base.a and libfltk_gl.a).