Add the basics for _browser_ (ecma)scripting ELinks with SEE

Add the basics for _browser_ (ecma)scripting ELinks with SEE

SEE is David Leonard's Simple Ecmascript Engine.  The SEE scripting backend
is very raw and not tested very much. The idea was to see what kind of
creature SEE is (and contradict pasky's aired opinion that no new features
are added anymore ;).

echo 'function goto_url() { return 'localhost'; }' > ~/.elinks/hooks.js
and get local for maximum security ...

FYI: SEE is smaller than Spidermonkey but doesn't have the same kind of
data-driven interface, although it looks like it is possible to build that.