[CM] Snd 17.7

[bil at ccrma.Stanford.EDU]

Snd 17.7:

Mike Scholz provided changes for Ruby 2.5.

s7: changed various "object" names to "c_object" in s7.h ("object" was 
ambiguous)
     c-pointers can participate in the generic function stuff
     gtkex.scm
     json.scm (aimed at the Language Server Protocol, eventually in emacs 
perhaps)

checked: gtk 3.91.2, sbcl 1.3.21

Thanks!: Kjetil Mattheussen, Mike Scholz