save_vrml(outname,[options],s1,...)    - Save vrml code

Makes a vrml2 file from strings of vrml code. A "background" node is
added.

Options :
"nobg"
"nolight"

Bugs :
- "outname" should not contain the substring ".wrl" anywhere else
than as a suffix.
- "outname" should only contain the character ">" as ">>" at the
beginning , to indicate append rather than overwriting the
file.