fix an overlap in parameter definitions
ft_sigintr(), reorder, side effect: if `ft_setflag' then gr_clean() won't be invoked

and can't be invoked anyway
  from inside of the signal handler
abstraction, introduce ft_sigintr_cleanup()
execute ft_sigintr_cleanup() outside of the signal handler

to avoid execution of non-reentrant functions
inp_stripcomments_line(), drop support for '--' comment style

seems to be not common in the spice world,
and interferes too much with mathematical expressions like
   {3--2}
inpcom.c: avoid segfault when `TABLE' is used without parentheses
gettok_node(), avoid segfault when *s == NULL
gettok_node(), use copy_substring()
inpcom.c: patch provided by Simon Chang: correct function name substitution
inpcom.c: patch provided by Simon Chang: correct function name substitution #2
inpcom.c: allow special characters in function names
inpcom.c: '$' as end-of-line comment delimiter
outside of .control section,
'$ ' inside of .control section