Fix 1214: cueDuring and quoteDuring should also quote voices that create subvoices

input/regression/quote-during-subvoice.ly

Index: input/regression/quote-during-subvoice.ly
diff --git a/input/regression/quote-during-subvoice.ly b/input/regression/quote-during-subvoice.ly
new file mode 100644
index 0000000000000000000000000000000000000000..6b39f07a27fd39bc5e0fde3e14f29eab5bca2e3c
--- /dev/null
+++ b/input/regression/quote-during-subvoice.ly
@@ -0,0 +1,68 @@
+\version "2.15.9"
+
+\header {
+  texidoc = "@code{\\quoteDuring} and @code{\\cueDuring} shall properly quote
+voices that create a sub-voice.  The sub-voice will not be quoted, though.
+Exceptions are sections of parallel music @code{<< @{...@} \\ @{...@} >>},
+which will be quoted.
+"
+}
+
+% Simple case, normal sub-voice
+quoteMe = \relative c' {
+  c4 c
+  \new Voice {
+    c4 c
+  }
+}
+\addQuote "quoteMe" \quoteMe
+% Also works if wrapped with \new Voice
+\addQuote "quoteMeA" \new Voice \quoteMe
+
+% Also works with voice directly inside relative
+quoteMeI = \relative c' \new Voice {
+  c4 c4
+}
+\addQuote "quoteMeI" \quoteMeI
+
+% Quoting music with some parallel sections (identical rhythm)
+quoteMeII = \relative c' {
+  c4 c
+  << { d4 e4 } \\ { c4 b4 } >>
+  c4
+}
+\addQuote "quoteMeII" \quoteMeII
+
+% Quoting music with some parallel sections (different rhythm)
+quoteMeIII = \relative c' {
+  c4 c
+  << { d4 e4 } \\ { c4. b8 } >>
+  c4
+}
+\addQuote "quoteMeIII" \quoteMeIII
+
+
+
+
+<<
+  \new Staff \relative c'' {
+    c4 \cueDuring #"quoteMe" #DOWN { r4 }
+    c4 \cueDuring #"quoteMe" #DOWN { r4 } % <- no cue note due to sub-voice
+  }
+  \new Staff \relative c'' {
+    c4 \cueDuring #"quoteMeA" #DOWN { r4 }
+    c4 \cueDuring #"quoteMeA" #DOWN { r4 } % <- no cue note due to sub-voice
+  }
+  \new Staff \relative c'' {
+    c4 \cueDuring #"quoteMeI" #DOWN { r4 }
+    c4
+  }
+  \new Staff \relative c'' {
+    c4 \cueDuring #"quoteMeII" #DOWN { r4 }
+    c4 \cueDuring #"quoteMeII" #DOWN { r4 } % <- quoted parallel notes
+  }
+  \new Staff \relative c'' {
+    c4 \cueDuring #"quoteMeIII" #DOWN { r4 }
+    c4 \cueDuring #"quoteMeIII" #DOWN { r4 } % <- quoted parallel notes
+  }
+>>