Manpages of lilypond in Debian stretch-backports

• abc2ly(1)
• convert-ly(1)
• etf2ly(1)
• lilymidi(1)
• lilypond-book(1)
• lilypond-invoke-editor(1)
• lilypond(1)
• lilysong(1)
• midi2ly(1)
• musicxml2ly(1)