use CharStream instead of ANTLRInputStream

src/main/java/de/hsrm/compiler/Klang/Klang.java

@@ -7,7 +7,7 @@ import org.antlr.v4.runtime.tree.*;
 public class Klang {
   public static void main(String[] args) throws Exception {
     // create a CharStream that reads from standard input
-    ANTLRInputStream input = new ANTLRInputStream(System.in);
+    CharStream input = CharStreams.fromStream(System.in);
 
     // create a lexer that feeds off of input CharStream
     KlangLexer lexer = new KlangLexer(input);