\version "2.19.80"
\include "ly-utility.ily"

#(define modernise-apostrophes? #f)
replaceDoubleApostrophes =
#(define-music-function (mus)(ly:music?)
   (music-map
    (lambda (m)
      (if (music-is-of-type? m 'lyric-event)
          (let ((txt (ly:music-property m 'text))
                (replacement (if modernise-apostrophes? "" "’")))
            (if (string? txt)
                (begin
                 (ly:music-set-property! m 'text
                   (make-replace-markup
                    (list (cons "’’" replacement))
                    txt))
                 m)
                m))
          m))
    mus))
\addToplevelMusicFunctions replaceDoubleApostrophes

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  \addlyrics { test’’ }
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