Adding version number to so name of libwebp for dllmap, there is no unversion version of libwebp available.

MediaBrowser.Server.Mono/Imazen.WebP.dll.config

@@ -1,4 +1,4 @@
 <configuration>
   <dllmap dll="libwebp" target="./libwebp/osx/libwebp.5.dylib" os="osx"/>
-  <dllmap dll="libwebp" target="libwebp.so" os="linux"/>
-</configuration>
+  <dllmap dll="libwebp" target="libwebp.so.5" os="linux"/>
+</configuration>