[CM] Snd 17.5

[bil at ccrma.Stanford.EDU]

Snd 17.5:

s7: s7_history and s7_add_to_history (Kjetil's suggestion).
     (*s7* 'history) for non-error scheme-side access to the history info
     lambda* keyword argument handling changed slightly.
     multithread sanity-checks thanks to Kjetil.
     Kjetil also ported s7 to mingw.

checked: gtk 3.91.0, sbcl 1.3.18, FC 26 (gcc 7.1.1)

Thanks!: Kjetil Matheussen, Rick Taube