elinks.keymaps.main["/"] = null;
used to crash ELinks with a segfault in JS_ObjectIsFunction.
Fix that by recognizing JSVAL_NULL explicitly and treating it as "none".
Likewise, if keymap_get_property would return "none" to ECMAScript,
return JSVAL_NULL instead.
Also document elinks.vs and elinks.action.
<kahmalo> Miciah: IMO most of contrib/smjs/README should be moved into
the ELinks manual. Specifically the parts that do not depend on
contrib/smjs/hooks.js. However manual.txt contains a notice:
"Hold blameless the authors. Any lawful use is allowed." Will
you allow that also for what is now in contrib/smjs/README?
<Miciah> Absolutely.
<Miciah> In fact, I would allow some lawless uses.
<Miciah> It seems a little silly to say that lawful uses are allowed.
