Minor changes

src/Todo

@@ -2,6 +2,7 @@ Library Features:
 + Thumbnail support: set (re-calculate)
 + operator>> for Value, since we already have read()?
 + Use auto_ptr where applicable
++ Use size_t where appropriate
 + Support TIFF type ids
 + Support for broken IFD makernotes (which have corrupted IFD offsets)
 + Support TIFF images (TiffImage)
@@ -14,6 +15,8 @@ Exiv2 functionality
 + Add offset to value for hexdump (requires metadata to have an offset)
 
 Bugs:
++ ExifData::copyFromMetadata: wrong offsets if no ExifTag exists. Same problem
+  probably occurs when GPSTag or InteroperabilityTag are missing.
 + Handle all Todo's
 + Cleanup and fix implementation of JpegImage (must be able to read any APP0/1),
   should be able to insert exv into extracted thumbs (usually w/o APP0/1)