fix build without VOIP (David Severwright, bug#3720)

code/client/cl_scrn.c

@@ -343,6 +343,7 @@ void SCR_DrawDemoRecording( void ) {
 }
 
 
+#ifdef USE_VOIP
 /*
 =================
 SCR_DrawVoipMeter
@@ -381,6 +382,7 @@ void SCR_DrawVoipMeter( void ) {
 	sprintf( string, "VoIP: [%s]", buffer );
 	SCR_DrawStringExt( 320 - strlen( string ) * 4, 10, 8, string, g_color_table[7], qtrue, qfalse );
 }
+#endif