Use our own ~s ly:format placeholder, since guile is broken with wide chars

[joeneeman]

http://codereview.appspot.com/109070/diff/1/2
File lily/general-scheme.cc (right):

http://codereview.appspot.com/109070/diff/1/2#newcode437
Line 437: replace_all (&s, "\"", "\\\"");
Don't forget to escape $. Or else use single quotes rather than double
quotes.

http://codereview.appspot.com/109070