version.cpp: remove useless header inclusion

The inclusion of link.h header is not required and can create build
error with some toolchains.
The patch is pushed on the upstream for the next release.
http://dev.exiv2.org/issues/1007

Signed-off-by: Nicolas Serafini <nicolas.serafini@sensefly.com>

--- exiv2-0.24.orig/src/version.cpp	2013-12-01 13:13:42.000000000 +0100
+++ exiv2-0.24/src/version.cpp	2014-12-04 09:30:39.667234130 +0100
@@ -116,7 +116,6 @@ typedef string_v::iterator  string_i;
 #elif defined(__linux__)
 # include <unistd.h>
 // http://syprog.blogspot.com/2011/12/listing-loaded-shared-objects-in-linux.html
-# include "link.h"
 # include <dlfcn.h>
   struct something
   {