added %option ignore_unused to suppress warnings about unused vars and subs in that module/block.

Also improved error for invalid directive.

codeCore/src/prog8/code/ast/AstBase.kt

@@ -86,6 +86,7 @@ class PtBlock(name: String,
                   val forceOutput: Boolean = false,
                   val noSymbolPrefixing: Boolean = false,
                   val veraFxMuls: Boolean = false,
+                  val ignoreUnused: Boolean = false,
                   val alignment: BlockAlignment = BlockAlignment.NONE)
 }