- Renamed 'xmlrpc_decode' to '_xmlrpc_decode' to avoid redeclaration when
  PHP's XML-RPC library is enabled.

- Renamed 'xmlrpc_encode' to '_xmlrpc_encode' to avoid redeclaration when
  PHP's XML-RPC library is enabled.

- Removed 'if (funcion_exist("xmlrpc_encode"))' check from common.inc.