Update akode seek method semantics.

Signed-off-by: Slávek Banko <slavek.banko@axis.cz>
Signed-off-by: Michele Calgaro <michele.calgaro@yahoo.it>

akode_artsplugin/arts_inputstream.h

@@ -75,8 +75,8 @@ public:
     long write(const char*, long) {
         return -1;
     }
-    bool seek(long to, int whence) {
-        if(!m_open || !seekable()) return false;
+    ssize_t seek(long to, int whence) {
+        if(!m_open || !seekable()) return -1;
 
         arts_debug("akode: InputStream seeking");
 
@@ -89,21 +89,21 @@ public:
                 newpos = m_pos + to;
                 break;
             case SEEK_END:
-                if (m_len < 0) return false;
+                if (m_len < 0) return -1;
                 newpos = m_len + to;
                 break;
             default:
-                return false;
+                return -1;
         }
 
-        long s = m_instream.seek(newpos);
+        ssize_t s = m_instream.seek(newpos);
         if (s >= 0) {
             m_pos = s;
             m_buffer->flush();
-            return true;
+            return s;
         }
         else
-            return false;
+            return -1;
     }
 
     long position() const {