[gexiv2] iostream: Adapt to new Exiv2 API in 0.26

[Jens Georg <jensgeorg src gnome org>]

commit f295c5ce9d0a87ee0c2cc793ca191369e05b7cf1
Author: Jens Georg <mail jensge org>
Date:   Fri May 12 19:50:58 2017 +0200

    iostream: Adapt to new Exiv2 API in 0.26
    
    https://bugzilla.gnome.org/show_bug.cgi?id=782449

 gexiv2/gexiv2-stream-io.cpp |    4 ++--
 gexiv2/gexiv2-stream-io.h   |    8 +++++++-
 2 files changed, 9 insertions(+), 3 deletions(-)
---
diff --git a/gexiv2/gexiv2-stream-io.cpp b/gexiv2/gexiv2-stream-io.cpp
index 0ae3324..abfb843 100644
--- a/gexiv2/gexiv2-stream-io.cpp
+++ b/gexiv2/gexiv2-stream-io.cpp
@@ -142,7 +142,7 @@ long StreamIo::tell () const {
     return cb->Position (cb->handle);
 }
 
-long StreamIo::size () const {
+StreamIo::size_type StreamIo::size () const {
     return cb->Length (cb->handle);
 }
 
@@ -175,7 +175,7 @@ Exiv2::DataBuf StreamIo::read (long read_count) {
 
 long StreamIo::read (Exiv2::byte* buf, long read_count) {
     long total_read_bytes = 0;
-    
+
     while (read_count > total_read_bytes) {
         /* because of a marshalling problem on managed side, we shift the
            pointer and do NOT use the offset parameter */
diff --git a/gexiv2/gexiv2-stream-io.h b/gexiv2/gexiv2-stream-io.h
index 76621a9..a26f4e6 100644
--- a/gexiv2/gexiv2-stream-io.h
+++ b/gexiv2/gexiv2-stream-io.h
@@ -25,6 +25,12 @@ public:
 
        StreamIo (ManagedStreamCallbacks* cb);
 
+#if EXIV2_TEST_VERSION(0,26,0)
+    typedef size_t size_type;
+#else
+    typedef long size_type;
+#endif
+
        virtual ~StreamIo ();
        virtual int open ();
        virtual int close ();
@@ -39,7 +45,7 @@ public:
        virtual Exiv2::byte* mmap (bool isWriteable = false);
        virtual int munmap ();
        virtual long tell () const;
-       virtual long size () const;
+       virtual size_type size () const;
        virtual bool isopen () const;
        virtual int error () const;
        virtual bool eof () const;