lex.ll: Accept block comments at the command prompt (bug #64903)

* lex.ll: Previously, the end of a block comment was also treated
as the end of a statement, which prevented loops with block comments
inside from being copy-pasted at the command prompt.  This patch
accepts block comments without ending the statement.

libinterp/parse-tree/lex.ll

@@ -784,16 +784,17 @@ ANY_INCLUDING_NL (.|{NL})
 
     curr_lexer->m_block_comment_nesting_level--;
 
-    int status = -1;
-
     if (curr_lexer->m_block_comment_nesting_level == 0)
       {
-        status = -2;
-
         curr_lexer->pop_start_state ();
-      }
 
-    HANDLE_EOB_OR_EOF (status);
+        if (curr_lexer->pending_token_count () > 0)
+          HANDLE_EOB_OR_EOF (-1);
+        else
+          HANDLE_EOB_OR_EOF (-2);
+      }
+    else
+      HANDLE_EOB_OR_EOF (-1);
   }
 
 %{