[CM] Snd 15.6

[Bill Schottstaedt]

Snd 15.6:

add int-vector? int-vector make-int-vector

changed s7_copy arg interpretation (it's now a normal s7_function).

checked: gtk 3.16.1|2 3.17.1, FC 22 (gcc 5), Ruby 2.2, sbcl 1.2.11

Thanks!: Tito Latini (found and fixed many bugs), 
         Donny Ward (MS Visual Studio 2013)