Uses one-based indices for columns.

We accidentally converted to zero-based indices with the last fix
where we moved a postfix increment to the location where it was used.

Therefore we have to turn this into a prefix increment.

src/main/java/parsii/tokenizer/LookaheadReader.java

@@ -51,7 +51,7 @@ protected Char fetch() {
             if (character == -1) {
                 return null;
             }
-            Char result = new Char((char) character, line, pos++);
+            Char result = new Char((char) character, line, ++pos);
             if (character == '\n') {
                 line++;
                 pos = 0;