This patch allows us to build libextractor against exiv2 0.27.x.
Adapted from this upstream commit:

  commit 1ecee9a47717e36cb8a3925d011d1a6de11d631c
  Author: Christian Grothoff <christian@grothoff.org>
  Date:   Mon Jul 29 17:58:18 2019 +0200

      importing patch from Gentoo/AS to address exiv2 build issue (#5820)

diff --git a/src/plugins/exiv2_extractor.cc b/src/plugins/exiv2_extractor.cc
index 8741d40..ef402a8 100644
--- a/src/plugins/exiv2_extractor.cc
+++ b/src/plugins/exiv2_extractor.cc
@@ -27,10 +27,7 @@
 #include <cassert>
 #include <cstring>
 #include <math.h>
-#include <exiv2/exif.hpp>
-#include <exiv2/error.hpp>
-#include <exiv2/image.hpp>
-#include <exiv2/futils.hpp>
+#include <exiv2/exiv2.hpp>
 
 /**
  * Enable debugging to get error messages.
@@ -180,7 +177,7 @@ public:
    *
    * @return -1 on error
    */
-#if EXIV2_VERSION >= EXIV2_MAKE_VERSION(0,26,0)
+#if EXIV2_TEST_VERSION(0,26,0)
   virtual size_t size (void) const;
 #else
   virtual long int size (void) const;
@@ -316,7 +313,11 @@ Extracto</td></tr></table>
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EXIV2_VERSION
+#if !EXIV2_TEST_VERSION(0,24,0)
       Exiv2::LogMsg::setLevel (Exiv2::LogMsg::mute);
 #endif
       std::auto_ptr<Exiv2::BasicIo> eio(new ExtractorIO (ec));