Added experimental bool ExifData::hasMakerNote() method

src/exif.cpp

@@ -899,6 +899,15 @@ namespace Exiv2 {
         return rc;
     } // ExifData::stdThumbPosition
 
+    bool ExifData::hasMakerNote() const
+    {
+        const_iterator e = end();
+        for (const_iterator md = begin(); md != e; ++md) {
+            if (ExifTags::isMakerIfd(md->ifdId())) return true;
+        }
+        return false;
+    } // ExifData::hasMakerNote
+
     ByteOrder ExifData::byteOrder() const
     { 
         if (pTiffHeader_) return pTiffHeader_->byteOrder();

src/exif.hpp

@@ -717,6 +717,10 @@ namespace Exiv2 {
           @brief Returns the byte order. Default is little endian.
          */
         ByteOrder byteOrder() const;
+        /*!
+          @brief Returns true if at least one makernote tag exists, else false.
+         */
+        bool hasMakerNote() const;
         /*!
           @brief Write the thumbnail image to a file. A filename extension
                  is appended to \em path according to the image type of the